Efecto de la frecuencia de ordeño sobre la producción

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Efecto de la frecuencia de ordeño sobre la producción
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias
Efecto de la frecuencia de ordeño
sobre la producción,
fraccionamiento lechero y
parámetros de calidad
de la leche en las cabras canarias
Alexandr Torres Krupij
Octubre 2013
Anexo II
UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA
Departamento: Instituto Universitario de Sanidad Animal y Seguridad
Alimentaria
Programa de Doctorado: Sanidad Animal
Título de la Tesis
“EFECTO DE LA FRECUENCIA DE ORDEÑO SOBRE LA
PRODUCCIÓN, FRACCIONAMIENTO LECHERO Y PARÁMETROS
DE CALIDAD DE LA LECHE EN LAS CABRAS CANARIAS”
Tesis Doctoral presentada por D. Alexandr Torres Krupij
Dirigida por los Dres. D. Anastasio Argüello Henríquez y D. Juan Capote Álvarez
El Director,
Anastasio Argüello Henríquez
El Director,
Juan Capote Álvarez
El Doctorando,
Alexandr Torres Krupij
Las Palmas de Gran Canaria, a 15 de julio de 2013
ANASTASIO ARGÜELLO HENRÍQUEZ, PROFESOR TITULAR DE
UNIVERSIDAD EN EL DEPARTAMENTO DE PATOLOGÍA ANIMAL,
PRODUCCIÓN ANIMAL, BROMATOLOGÍA Y TECNOLOGÍA DE LOS
ALIMENTOS
DE
LA
FACULTAD
DE
VETERINARIA
DE
LA
UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA
INFORMA:
Que Alexandr Torres Krupij, Ingeniero Químico, ha realizado bajo mi
dirección y asesoramiento el presente trabajo titulado “EFECTO DE LA
FRECUENCIA
DE
ORDEÑO
SOBRE
LA
PRODUCCIÓN,
FRACCIONAMIENTO LECHERO Y PARÁMETROS DE CALIDAD
DE LA LECHE EN LAS CABRAS CANARIAS” considerando que reúne
las condiciones y calidad científica para optar al grado de Doctor en
Veterinaria.
Las Palmas de Gran Canaria, julio 2013
Fdo. Anastasio Argüello Henríquez
JUAN
CAPOTE
ÁLVAREZ,
DIRECTOR
DE
LA
UNIDAD
DE
PRODUCCIÓN ANIMAL, PASTOS Y FORRAJES DEL INSTITUTO
CANARIO DE INVESTIGACIONES AGRARIAS
INFORMA:
Que Alexandr Torres Krupij, Ingeniero Químico, ha realizado bajo mi
dirección y asesoramiento el presente trabajo titulado “EFECTO DE LA
FRECUENCIA
DE
ORDEÑO
SOBRE
LA
PRODUCCIÓN,
FRACCIONAMIENTO LECHERO Y PARÁMETROS DE CALIDAD
DE LA LECHE EN LAS CABRAS CANARIAS” considerando que reúne
las condiciones y calidad científica para optar al grado de Doctor en
Veterinaria.
Las Palmas de Gran Canaria, julio 2013
Fdo. Juan Capote Álvarez
FACULTAD DE VETERINARIA
TESIS DOCTORAL
EFECTO DE LA FRECUENCIA DE ORDEÑO
SOBRE LA PRODUCCIÓN,
FRACCIONAMIENTO LECHERO
Y PARÁMETROS DE CALIDAD DE LA LECHE
EN LAS CABRAS CANARIAS
Alexandr Torres Krupij
Las Palmas de Gran Canaria, Octubre 2013
AGRADECIMIENTOS
Ni en estas líneas ni en un libro entero puedo plasmar mi gratitud a las personas e instituciones que han hecho posible la realización de esta tesis. Soy de los que prefieren
mostrar cotidianamente mi agradecimiento de muchas formas, sin necesidad de esperar
al final para enumerar una a una las personas que han sido importantes en este trabajo.
Sin embargo, me gustaría mencionar:
• Al INIA por la oportunidad de financiar mi doctorado, sin lo cual, hubiese
sido prácticamente imposible continuar con la formación.
• Muchas gracias al equipo de trabajo del Departamento de Producción
Animal de la ULPGC y a la Unidad de Producción Animal, Pastos y Forrajes
del ICIA. A los “jefes” de dichos grupos, por mostrarme las directrices
a seguir y contribuir a lograr los objetivos pautados. A mis compañeros
de laboratorio (estudiantes y personal técnico) por brindarme su amistad
y ayuda desinteresada. Por compartir tantos momentos agradables. Me
siento orgulloso de haber pertenecido a estos grupos.
• Especialmente gracias al personal de la Escuela de Capacitación Agraria
de Arucas, por hacer que mi estancia fuese tan entrañable, fueron como
una familia para mí y nunca los olvidaré.
• Por último, mención especial a esas personas, que aunque no pertenezcan a este mundo de cabras, experimentos-resultados y papers, me animaron en su momento a empezar un doctorado, a continuar cuando las
fuerzas disminuían, y a darme el empujón final con alegría y esperanza.
Gracias de corazón.
Textos:
Instituto Canario de Investigaciones Agrarias.
Finca “Isamar”, Ctra. de El Boquerón s/n, Valle Guerra. La Laguna. Tenerife. 38270.
Facultad de Veterinaria de la Universidad de Las Palmas de Gran Canaria.
Campus Universitario de Arucas. Arucas. 35416.
Diseño y cuidado editorial
Mónica Pedrós
Fotografía de portada
Fermín Correa
INDICE
INTRODUCCIÓN
21
ARTÍCULO 1
69
ARTÍCULO 2
75
MANUSCRITO 3
83
MANUSCRITO 4
103
MANUSCRITO 5
123
CONCLUSIONES
145
INTRODUCCIÓN
INTRODUCCIÓN
1. El sector caprino
1.1. El caprino a nivel mundial
1.1.1. Generalidades
La cabra fue de los primeros animales domesticados por el hombre, hace unos 10500 años,
contribuyendo al desarrollo de la agricultura durante el periodo neolítico (Fernández y col., 2006).
Desde entonces entró a formar parte de la alimentación del ser humano, proporcionándole leche
y carne, además de piel, pelo y estiércol (Vigne y Helmer, 2006). La importante contribución de la
ganadería caprina al sostenimiento alimentario de la humanidad ha hecho que en la actualidad se
encuentre en regiones geográficas que difieren notablemente en clima, topografía y fertilidad, debido
a su gran rusticidad y adaptabilidad (Devendra, 1987).
Las cabras pueden adaptarse a una amplia gama de sistemas de intensificación que van de
un extremo al otro: por un lado, las razas lecheras mejoradas explotadas en condiciones intensivas
en las zonas templadas de Europa o América del Norte, en ciertas zonas favorables de clima tropical
húmedo, o en superficies irrigadas de clima tropical seco y, por otro lado, las poblaciones locales que
se mantienen en regiones muy áridas en las que los demás rumiantes difícilmente pueden resistir,
tales como las zonas desérticas de África o del Medio Oriente (Boyazoglu y Morand-Fehr, 1987).
1.1.2. Población caprina y producción lechera
La población caprina a nivel mundial ha incrementado su censo de forma importante durante
los últimos 40 años, mucho más que los censos de bovino y ovino (Tabla 1), lo cual sugiere el creciente
interés por parte de la población en los productos lácteos derivados de la cabra (Dubeuf, 2005).
Tabla 1. Población mundial de bovino, ovino y caprino en los últimos 40 años (millones de cabezas).
(FAOSTAT, 2011).
Año
2010
2000
1990
1980
1970
Bovino
1427,5
1313,2
1298,4
1217,0
1081,6
Ovino
1078,3
1059,7
1207,9
1098,7
1063,3
21
Caprino
909,8
751,4
591,1
464,3
377,7
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Sin embargo, la distribución del caprino es bastante desigual a nivel mundial. Según la Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO), en el año 2011 Asia
concentraba el 61,6% del censo total, mientras que África contaba con el 31,6%. En contraste, Europa
y América sólo tienen el 1,9% y 4,3%, respectivamente. Así, países como China, India, Pakistán, Bangladesh, y Nigeria (Figura 1) están a la cabeza en cuanto a población de cabras, representando un
valioso sustento para numerosas familias de escasos recursos.
Figura 1. Principales países en población caprina en el año 2011. (FAOSTAT, 2011).
De acuerdo con la FAO, la producción de leche de cabra en el mundo durante el año 2011 fue
de aproximadamente 15 millones de toneladas, lo que representó el 2,2% del total de la leche producida a nivel mundial. Europa, con sólo el 5% del total del ganado caprino lechero, produjo casi el 20%
del volumen de leche total de esta especie. Cabe señalar, que en algunos países de África y Asia, las
estadísticas no registran el verdadero valor de la producción, debido a la dificultad para hacer los
censos, por la dispersión de los rebaños, y porque prácticamente toda la leche se destina al consumo
de la unidad familiar.
1.1.3. Biodiversidad caprina
Entre los 900 millones de cabras a nivel mundial, un total de 570 razas han sido definidas. Los
países en vías de desarrollo concentran el 60% del total de las razas (Galal, 2005). En Europa se encuentran los genotipos con mayor producción lechera como la Saanen, Alpina, Nubia o Toggenburg
(Figura 2). Sin embargo este continente posee la menor diversidad genética, debido a los procesos de
mejora productiva, en los que han desaparecido las razas menos competitivas.
22
INTRODUCCIÓN
Figura 2. Principales razas caprinas lecheras. A: Saanen; B: Alpina; C: Nubia; D: Toggenburg. (Breed Standards,
www.dairygoatjournal.com).
1.2. El caprino en España
1.2.1. Generalidades
Durante muchos años, la cabra en España ha jugado un destacado papel en el abastecimiento
de leche para el consumo de la población. La leche obtenida era destinada al consumo familiar, mayoritariamente de forma directa, aunque una fracción variable según casos, era transformada en queso,
elaborado en la propia explotación por métodos artesanales (Esteban-Muñoz, 2008). La ganadería
caprina ha estado ligada tradicionalmente a zonas rurales poco productivas desde el punto de vista
agrícola, dado que las cabras tienen una gran capacidad para el aprovechamiento de los pastos de
escasa calidad. Esta característica ha hecho que el ganado caprino jugase un papel importante en el
mantenimiento de zonas marginales y de la población asociada a ellas. Aún hoy en día, en España, el
86% de la población caprina se encuentra en las llamadas áreas menos favorecidas (Rancourt y col.,
2006), aunque los sistemas de explotación han cambiado sustancialmente.
1.2.2. Población caprina y producción lechera
En España, según la FAO, la población de caprinos de aptitud lechera se estimó alrededor de
los 1,2 millones de cabezas en el año 2011. La evolución del censo caprino en los últimos 20 años (Figura 3) ha sufrido oscilaciones significativas, como consecuencia, entre otros aspectos, de la variabilidad en los precios de la leche. Sin embargo, la producción lechera sobrepasó las 540000 toneladas
en el 2011, con un incremento anual medio del 4% durante las últimas dos décadas, principalmente
debido a la mejora genética y alimenticia, lo cual ha permitido optimizar el rendimiento lechero.
23
Miles de cabezas de ganado Miles de cabezas de ganado Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
2000 1000 1600 800 2000 1200 1000 600 1600 800 800 400 1200 400 600 200 1991 800 1995 1999 2003 Año 2007 2011 400 400 200 Ganado caprino lechero Producción lechera 1991 1995 1999 2003 2007 2011 Miles dde e tloneladas de leche Miles de toneladas eche Introducción
Introducción
Año Figura 3. Evolución del ganado caprino lechero y producción de leche de cabra en España en los últimos
Ganado c20
aprino lechera años.lechero (FAOSTAT,Producción 2011).
Figura
3. Evolución
del ganado
caprino
lechero
y producción
de leche
de cabra
España
últimos
Figura
3. Evolución
del ganado
caprino
lechero
y producción
de leche
de cabra
en en
España
en en
loslos
últimos
20 años.
(FAOSTAT, 2011).
La distribución del caprino
en la(FAOSTAT,
geografía española
es muy irregular (Figura 4).
20 años.
2011).
En La
Canarias
y en eldelsur
de la Península
Ibéricaespañola
se concentra
alrededor
80% del
censo
distribución
caprino
en la geografía
es muy
irregulardel
(Figura
4). En
Canarias y
en elde
surcabras.
de La
la Península
Ibérica
sedeconcentra
alrededor
del 80%
censo
de cabras.
La larga
distribución
del caprino
la geografía
española
esgeográficas
muy
irregular
4). tradiLa
larga tradición
losencabreros
de dichas
áreasdel
y la(Figura
presencia
ción de los cabreros de dichas áreas geográficas y la presencia de razas caprinas de alta producción
Enrazas
Canarias
y en de
el sur
la Península
se concentra
alrededor agroclimática,
del 80% del censo
de
caprinas
altadeproducción
de Ibérica
leche, además
de la situación
han
de leche, además de la situación agroclimática, han favorecido el desarrollo del caprino en estas
de cabras.
La
larga tradición
de losen
cabreros
de dichas
áreas geográficas
y la presencia
favorecido
el desarrollo
del caprino
estas regiones
(Esteban-Muñoz,
2008).
regiones
(Esteban-Muñoz,
2008).
de razas caprinas de alta producción de leche, además de la situación agroclimática, han
favorecido el desarrollo del caprino en estas regiones (Esteban-Muñoz, 2008).
Figura
4. Distribución
deldel
ganado
caprino
porpor
comunidades
autónomas
en 2011.
(MAGRAMA,
Figura
4. Distribución
ganado
caprino
comunidades
autónomas
en 2011.
(MAGRAMA,2011).
2011).
Figura 4. Distribución del ganado caprino por comunidades autónomas en 2011. (MAGRAMA, 2011).
24
Página 9 leche de cabra, con más del 40% del total español, seguida por Canarias y Castilla La
Mancha (Figura 5). La leche de cabra que se obtiene se destina mayoritariamente a la
fabricación de queso, y en menor medida al consumo directo. Según datos INTRODUCCIÓN
del
Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA), en el año
2010,
únicamente
el 40% defue
la la
leche
de cabraautónoma
recogida con
en mayor
Españaproducción
se destinó de
a la
En el
año 2011, Andalucía
comunidad
leche de
cabra,
con más del
40% del
totaldeespañol,
seguida
Canarias
y Castilla
La Mancha
(Figura
fabricación
de queso
puro
cabra, siendo
el por
resto
de la leche
destinada
a quesos
de 5). La
leche de cabra que se obtiene se destina mayoritariamente a la fabricación de queso, y en menor memezcla, otros productos fermentados o exportada a otros países. Se han identificado un
dida al consumo directo. Según datos del Ministerio de Agricultura, Alimentación y Medio Ambiente
(MAGRAMA),
el año puros
2010, únicamente
40% yde21lade
leche
de cabra
recogida
en España
se destinó
total de 28enquesos
de leche de el
cabra
mezcla
con leche
de oveja
y/o vaca
a la fabricación de queso puro de cabra, siendo el resto de la leche destinada a quesos de mezcla,
(Ramírez, 2009). Así, encontramos quesos típicos en Andalucía (Sierra de Cádiz,
otros productos fermentados o exportada a otros países. Se han identificado un total de 28 quesos
Quesitos
Zuheros,
Sierra
decon
Cazorla,
Murcia
(Murcia
al vino),
puros
de lechede
de cabra
y 21 de
mezcla
leche deMalagueño),
oveja y/o vaca
(Ramírez,
2009). Así,
encontramos
quesos
típicos en (Ibores),
Andalucía
(Sierra de(Majorero,
Cádiz, Quesitos
de Herreño),
Zuheros, Sierra
de Cazorla,
Malagueño),
Extremadura
y Canarias
Palmero,
entre otros.
En general,
Murcia (Murcia al vino), Extremadura (Ibores), y Canarias (Majorero, Palmero, Herreño), entre otros.
se trata de quesos de calidad donde la industria ha mantenido los tipos tradicionales y
En general, se trata de quesos de calidad donde la industria ha mantenido los tipos tradicionales y los
los criterios
de elaboración,
donde algunos
ellos
han accedido
a los mercados
criterios
básicos básicos
de elaboración,
donde algunos
de ellosde
han
accedido
a los mercados
internacionales con
éxito (Esteban-Muñoz,
2008).
internacionales
con éxito (Esteban-Muñoz,
2008).
Resto Castilla y
6%
León
7%
Canarias
19%
Castilla La
Mancha
13%
Murcia
7%
Andalucía
43%
Extremadura
5%
Figura 5. Distribución de la cantidad de leche producida por Comunidades Autónomas en el 2011. (MAGRAMA, 2011).
Figura 5. Distribución de la cantidad de leche producida por Comunidades Autónomas en el 2011.
(MAGRAMA, 2011).
1.2.3. Biodiversidad caprina
España cuenta con un patrimonio genético caprino que ocupa un lugar preferente en Europa.
La alta
a
capacidad de las razas autóctonas para producir leche en zonas desfavorecidas,
Página conduce
10 que la explotación de estos animales adquiera un significado especial en los campos económico y
25
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
social (Castel y col., 2010). El Real Decreto 2129/2008, de 26 de diciembre, establece el programa nacional de conservación, mejora y fomento de las razas ganaderas. En el mismo se definen a las razas
autóctonas caprinas como de fomento o de protección especial.
Las razas Murciano-Granadina y Malagueña (Figura 6) que junto con las razas Majorera, Palmera y Tinerfeña, se encuentran en expansión por su censo y organización, son las consideradas
como de fomento, mientras que el grupo de protección especial compuesto por otras 16 razas, entre
las que destacan la Payoya y la Florida, disponen en su conjunto de una población reducida, debido
a una menor producción lechera, al fuerte aumento de los costes de producción, además de los problemas relacionados con la escasez de cabreros (Esteban-Muñoz, 2008).
Figura 6. Cabras Murciano-Granadina (izquierda) y Malagueña (derecha). (MURCIGRAN y CABRAMA).
1.3. El caprino en las Islas Canarias
1.3.1. Generalidades
En Canarias, la explotación caprina ha constituido tradicionalmente un importante recurso económico que, en épocas prehispánicas, llegó a ser el más importante de los aborígenes (Figura 7) (Fresno
y col., 1992). El ganado que ellos manejaban, de origen desconocido hasta el momento, les servía como
fuente de alimentación (carne, leche) y les proporcionaba pieles, huesos e incluso productos con utilidad medicinal (manteca). Es de suponer que estos animales, constituían una raza rústica más o menos
uniforme, si bien existían por aquella época, dos tipos de ganado caprino, uno doméstico o “jairo”, y otro
salvaje o “guanil”, cuyos últimos ejemplares desaparecieron en la década de los cincuenta de su último
reducto: La Caldera de Taburiente en la isla de La Palma (Capote y col., 1993).
26
INTRODUCCIÓN
Figura 7. Mural de Antonio González Suárez sobre la vida aborigen en Canarias, en el salón de plenos del Ayuntamiento
de los Llanos de Aridane. (CRDOP Queso Palmero).
Desde finales del siglo XV, Canarias se convirtió en paso obligado para las rutas transoceánicas, lo que significó aportes genéticos a la población caprina ya existente. Así, se puede observar
en unas determinadas características (capas, cornamenta) la influencia que en su día tuvieron cabras portuguesas (Charnequeira, Serpentina), españolas (Pirenaica, Granadina), europeas (Saanen)
y africanas (Nubia), y que junto con las distintas condiciones medioambientales de cada isla (clima,
orografía, pastos), han terminado por configurar los tipos caprinos que hoy constituyen el archipiélago (Capote y col., 1998).
1.3.2. Población caprina y producción lechera
En la actualidad las cabras tienen un importante peso específico dentro del subsector ganadero, y su población está distribuida en todas las islas, aunque la mayor parte del censo se concentra
en Fuerteventura, Gran Canaria, y Tenerife (Tabla 2).
27
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Tabla 2. Distribución de la cabaña caprina por islas en el año 2010. (Instituto Canario de Estadística, 2010).
Isla
Nº Cabezas
116226
82742
61434
27651
24208
11175
10481
Fuerteventura
Gran Canaria
Tenerife
La Palma
Lanzarote
La Gomera
El Hierro
%
34,8
24,8
18,4
8,3
7,2
3,3
3,1
En las últimas décadas, el caprino de las islas se ha exportado a regiones mediterráneas y
tropicales donde se ha adaptado con bastante facilidad. Así, en países como Venezuela, la cabra
“Canaria” (Figura 8), que no es más que una amalgama de las tres razas de las islas, con predominancia de la raza Majorera, está muy bien valorada por los ganaderos que destacan su rusticidad y
alta productividad. Por ello, cerca del 95% de las explotaciones intensivas ubicadas en ese país emplean dicha raza (Torres y Capote, 2011). Adicionalmente, la reciente introducción de cabras de raza
Majorera en Senegal y los respectivos informes técnicos confirman la excelente adaptación de esas
cabras al medioambiente subsahariano (Capote y col., 2012).
Figura 8. Cabras, con cruce de Canaria, en una explotación ganadera en el estado Lara en Venezuela.
(Torres y Capote, 2011).
28
INTRODUCCIÓN
Según el Instituto Canario de Estadística, en 2010 se produjeron más de 85000 toneladas de
leche de cabra, cuya finalidad principal fue la producción de queso (Figura 9), la mayor parte del cual
se elabora con leche cruda usando métodos tradicionales y es consumido tras breves periodos de
maduración (7 días) (Fresno y col., 2008). Además de la riqueza genética caprina y forrajera, Canarias
tiene una excepcional situación sanitaria debido al estar oficialmente libre de brucelosis caprina y
ovina (Sánchez-Macías y col., 2011), lo cual permite a aproximadamente 500 productores artesanos
la venta de quesos de leche cruda con menos de 60 días de maduración (Fresno y Álvarez, 2007).
Destaca la elaboración de dos quesos puros de leche de cabra, Majorero y Palmero, y un queso de
mezcla de oveja con leche de vaca y/o cabra, el “Queso Flor de Guía y Queso de Guía” que poseen
Denominación de Origen Protegida (DOP), aunque en este último caso, la leche de cabra puede ser
utilizada en un 10% como máximo.
Figura 9. Quesos canarios. (ICCA).
1.3.3. Biodiversidad caprina
Hasta l985 todos los trabajos publicados incluían a los individuos de la población caprina canaria dentro de una raza en la que se admitían las más variadas morfologías. Durante ese mismo
año se publicó en el Boletín Oficial del Estado (BOE) la Orden por la que se aprobaban las normas
reguladoras del Libro Genealógico y de Comprobación de Rendimiento para la Agrupación Caprina
29
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Canaria, donde se eliminó el término “raza”. Capote (1985) postuló la hipótesis de la existencia de tres
razas diferenciadas, basada en la opinión de los ganaderos, y denominadas según su isla de origen:
Majorera (Fuerteventura), Palmera (La Palma), y Tinerfeña (Tenerife), si bien esta última podría estar
dividida en otras dos que se situarían en la franja Norte (húmeda) y Sur (árida) de la isla. Posteriormente, los estudios morfológicos (Capote y col., 1998) y genéticos (Martínez y col., 2006) confirmaron
dicha hipótesis. El reconocimiento de las tres razas (Figura 10) está recogido en el Catálogo Oficial de
Razas de Ganado de España (BOE, Orden APA 2420/2003, de 28 de agosto).
Figura 10. Razas caprinas canarias. A: Majorera; B: Palmera; C: Tinerfeña. (Gobierno de Canarias).
A continuación se describen las tres razas caprinas canarias reconocidas oficialmente:
∑ Raza Majorera.
Debe su nombre a la Isla de Fuerteventura (Maxorata en la época prehispánica) lugar donde
se formó y donde se encuentra el mayor núcleo de animales de la raza, aunque su cría se extiende por
todas las islas del archipiélago. En general, la cabra Majorera se adapta bien a los diferentes sistemas de explotación, desde el pastoreo en zonas áridas, a la estabulación permanente, con elevados
rendimientos en la producción de leche.
Existe coincidencia en admitir que cuando llegaron los castellanos a las islas, a finales del
siglo XV, existía una población caprina adaptada al medio que había permanecido aislada genéticamente del resto del mundo. Posteriormente, la llegada de nuevas etnias, incidieron sobre el fondo
genético de la población caprina prehispánica, dejando rasgos en la población actual de las islas y
que recuerdan a troncos como el Pirenaico o el Nubiano africano (Amills y col., 2004).
30
INTRODUCCIÓN
El prototipo racial responde a las siguientes características (Figura 11): Cabeza de tamaño
grande, con perfil fronto-nasal recto o subconvexo, con orejas grandes e inclinadas hacia abajo. Los
cuernos pueden ser tipo prisca o de tipo aegagrus, en arco hacia atrás. La línea dorso-lumbar es recta. El pelo se presenta generalmente uniforme, corto y raso, y capa policromada. Ubre de color negro
o pizarra, tipo globosa o abolsada, de amplia inserción, con pezones bien diferenciados y, a veces de
implantación lateral (Esteban-Muñoz, 2008).
Figura 11. Cabra Majorera. (FEAGAS).
La producción media de las cabras de raza Majorera es de 551,3 kg de leche en 210 días de
lactación. Por otra parte, un elevado porcentaje de cabras mantienen durante ese periodo una producción media superior a 2 kg de leche por día. Con una composición media de la leche de: Grasa =
3,94%; Proteína = 3,90%; Lactosa = 4,55%; Extracto Seco = 13,19% (Fresno, 1993).
Hay que tener en cuenta que una buena parte de la leche de estas cabras es destinada a la
elaboración de queso artesanal o industrial, el cual se consume después de unos días de oreo, o bien
se deja madurar largo tiempo, en ambiente templado y seco. El queso que se va a conservar más
tiempo puede untarse con aceite, pimentón y/o gofio, lo que le confiere características peculiares.
Su masa al corte aparece compacta, de textura cremosa y sabor acídulo y algo picante. Es de color
blanco, tomando un ligero tono marfileño en quesos curados (Fresno y Álvarez, 2007).
31
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
∑ Raza Palmera.
Tiene su origen en la población caprina prehispánica en la isla de La Palma. Al ser esta isla un
lugar de paso en las rutas veleras con destino a América, la raza Palmera se vio influenciada por las
razas del suroeste de la Península Ibérica. Sin embargo, este genotipo tuvo un mayor aislamiento que
las otras razas canarias, lo que la aproxima más a la cabra prehispánica, y sustenta su diferenciación
genética, que permite una extraordinaria rusticidad y capacidad de adaptación a zonas abruptas de
montaña (Martínez y col., 2006).
En la década de los setenta la raza experimentó cruces con animales pertenecientes a la población Majorera con objeto de aumentar la producción de leche, debido a la errónea política en ese
momento de considerar a las tres razas canarias como una sola. Aquellos cruzamientos implicaron un
trabajo posterior enorme y complicado, aunque afortunadamente con resultados satisfactorios, para
eliminar los genes foráneos ya que los híbridos no se adaptaban a las condiciones de explotación de
la Isla de La Palma (Capote y col., 1993).
El prototipo racial responde a las siguientes características (Figura 12): Cabeza de tamaño
pequeño, corta y ancha, con perfil fronto-nasal recto o subcóncavo, orejas más bien cortas y una
cornamenta destacada, con predominancia del tipo heteronima. Tronco largo, con línea dorso-lumbar
recta. En sus capas predomina el color rojizo y el pelo es de longitud media. Ubre más recogida que
en las otras razas canarias, de tipo globosa, color negro o pardo, y con pezones más bien pequeños
(Esteban-Muñoz, 2008).
Figura 12. Cabra Palmera. (CRDOP Queso Palmero).
32
INTRODUCCIÓN
La producción media tipificada a 210 días de lactación, es de 362,6 kg de leche, con una producción de gran persistencia, lo que permite ampliar el periodo de lactación a 240-270 días. La calidad
media de la leche es de: Grasa = 4,06%; Proteína = 4,21%; Lactosa = 4,66%; Extracto Seco = 13,75%
(Fresno, 1993).
La producción de leche de la cabra Palmera va destinada a la fabricación de queso de tipo
artesanal. Se trata de un queso graso o extragraso, elaborado con leche cruda y entera, y se comercializa tanto tierno (de 8 a 20 días), como semicurado (21 a 60 días) y curado (a partir de 60 días).
El sabor es franco y láctico, muy mantecoso y con un ligero y agradable aroma ahumado (Fresno y
Álvarez, 2007).
∑ Raza Tinerfeña.
Si bien en el Catálogo Oficial es considerada como una única población, estudios morfológicos y genéticos señalan suficientes evidencias para considerar dos grupos independientes en el
norte y sur de la isla de Tenerife (Capote y col., 1998; Martínez y col., 2006). Así, existiría el ecotipo
Norte, con gran influencia del tronco pirenaico, y el ecotipo Sur, reducido en pureza por sus cruces
con cabra Majorera. Al igual que las otras dos razas, la cabra Tinerfeña presenta una gran rusticidad
y elevada aptitud para la producción de leche.
El prototipo racial tiene las siguientes características (Figura 13): Cabeza de tamaño proporcionado con el cuerpo, el ecotipo Norte dispone de un perfil fronto-nasal recto o subconvexo, mientras que en el Sur casi siempre es recto. Ambas tienen cornamenta tipo prisca. Orejas de gran tamaño, inclinadas hacia abajo en las cabras del Norte, y de menor tamaño en cabras de la zona Sur. Los
caprinos del Norte se caracterizan por presentar pelo largo y colores oscuros, principalmente negro
y con alguna frecuencia castaño. Los caprinos del Sur tienen el pelo corto y disponen de una capa
multicolor. La ubre de estas cabras, en general presentan un tipo similar al de la cabra Majorera, con
pezones pequeños y situados con alguna frecuencia en posición lateral. En la cabra Tinerfeña Norte,
la forma de la ubre, frecuentemente globosa, es más adecuada para el ordeño mecánico en lo referente al tamaño y posición de los pezones, que su homóloga del Sur (Esteban-Muñoz, 2008).
Los valores asignados a la producción de leche de cabra Tinerfeña en 210 días de lactación,
es de 421,0 kg de leche, con una composición de: Grasa = 3,91%; Proteína = 3,79%; Lactosa = 4,46%;
Extracto Seco = 13,13% (Fresno, 1993). En la isla de Tenerife, se elabora el Queso de Tenerife, obtenido
33
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
con leche cruda de cabra. Se trata de un queso de graso a extragraso y que se consume preferentemente fresco o ligeramente curado, de color blanco intenso y brillante, y sabor muy fresco y acidulado, ligeramente salado y graso lechoso al paladar (Fresno y Álvarez, 2007).
Figura 13. Cabra Tinerfeña Norte. (ACRICATI).
2. La leche de cabra
En términos generales, la leche de cabra es un líquido blanco opaco, de un sabor ligeramente
azucarado, cuyo olor es poco marcado cuando es recogida con limpieza de animales que tengan un
buen estado de salud. La consistencia es uniforme sin grumos ni copos. De la calidad de la leche
empleada en queserías va a depender gran parte el éxito de las transformaciones y la calidad del
producto final. Nutricionalmente, la leche de cabra es una fuente de proteínas de alto valor biológico y ácidos grasos esenciales, además de minerales y vitamina A. Es de gran importancia para los
infantes por su alto valor nutricional, hipoalergenicidad, así como por su alta digestibilidad debido al
pequeño tamaño de los glóbulos de grasa. Algunos autores han resaltado las propiedades saludables
de la leche de cabra (Silanikove y col., 2010) y sus productos derivados (Ribeiro y Ribeiro, 2010), justificando su alta calidad y los beneficios de su consumo. Además, la población del mundo desarrollado
no se preocupa especialmente sobre el costo de los productos en el mercado si al consumir deriva-
34
INTRODUCCIÓN
dos lácteos de cabras puede obtener beneficios para la salud (Mowlen, 2005). Actualmente existen
revisiones que han profundizado en las características físico-químicas (Park y col., 2007), reológicas
(Park, 2007) e higiénico-sanitarias (Raynal-Ljutovac y col., 2007) de la leche de cabra.
2.1. Composición química
La leche está compuesta principalmente, además del agua, por materia grasa, proteínas,
lactosa, sales minerales, vitaminas, y enzimas. La composición varía apreciablemente de acuerdo a
algunos factores como la raza, la alimentación, el período de lactación, la frecuencia de ordeño, el
estado sanitario de la cabra, entre otros.
2.1.1. Grasa
El contenido de grasa es el componente más variable cuantitativa y cualitativamente en la
leche. Los glóbulos de grasa de la leche de cabra son en general más pequeños y más finos que en
la leche de vaca (3,5 vs. 4,6 µm, respectivamente) (Park, 2006). A causa de su reducido tamaño y la
uniformidad de su distribución, los glóbulos de la leche de cabra ingerida quedan más dispersos y,
como resultado, las enzimas digestivas humanas, al actuar sobre ellos, los desintegran de forma más
rápida y completa.
No se han encontrado diferencias apreciables en el mecanismo de secreción de los glóbulos
de grasa en cabra, oveja y vaca, teniendo estos glóbulos una estructura y composición similar entre
las tres especies (Scolozzi y col., 2003). Respecto a los ácidos grasos que forman parte de la leche
de cabra, cinco de ellos representan más del 75%: cáprico (C10:0), mirístico (C14:0), palmítico (C16:0),
esteárico (C18:0) y oleico (C18:1) (Chilliard y col., 2006).
2.1.2. Proteína
En cuanto a las proteínas de la leche, éstas se dividen habitualmente como caseínas y proteínas séricas, aunque se pueden encontrar otras proteínas minoritarias, como inmunoglobulinas,
lactoferrina, transferrina, ferritina, peptona proteasa, prolactina, etc. El contenido total de proteínas
es uno de los principales criterios de calidad usados como sistema de pago de la leche de cabra en
muchos países (Pirisi y col., 2007).
35
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
En general, la ß-caseína es la principal caseína en la leche de cabra (Tziboula-Clarke, 2003).
La proporción de las 4 caseínas mayoritarias en la leche de cabra está determinada por polimorfismos genéticos, pero en general el orden es ß-caseína > αS2-caseína > αS1-caseína > k-caseína. De
media, la αS1-caseína representa el 10% del total de las caseínas, variando de 0 a 25% (Boulanger y
col., 1984), dependiendo del genotipo del animal. Las razas caprinas canarias (Majorera, Tinerfeña y,
especialmente, Palmera) representan un caso particular donde el 60% de los alelos de la αS1-caseína
caprina son del tipo A y B (Jordana y col., 1996), por lo que esta caseína es relativamente abundante
en la leche y quesos elaborados a partir de estos animales.
2.1.3. Lactosa
La lactosa es el carbohidrato por excelencia en la leche, el cual está formado por una molécula de glucosa y otra de galactosa, que también pueden estar presentes de forma individual en
pequeñas cantidades libres (Park, 2006). La lactosa es de gran importancia para mantener el equilibrio osmótico entre la corriente sanguínea y las células alveolares de la glándula mamaria durante la
síntesis de la leche, y su secreción en el lumen alveolar y el sistema de conductos de la ubre (Park y
col., 2007). En cabra se suele encontrar sobre 0,2-0,5% menos que en la leche de vaca y oveja. Otros
carbohidratos presentes en la leche de cabra son los oligosacáridos, glicopéptidos, glicoproteínas y
nucleótidos (Park y col., 2007), pero sus funciones han sido muy poco estudiadas.
2.1.4. Vitaminas y minerales
El contenido de macrominerales en la leche de cabra es mucho mayor que el de la leche humana, con cuatro y seis veces más calcio y fósforo, respectivamente. Comparativamente, la leche de
cabra contiene más calcio, fósforo, potasio, magnesio y cloro, y menos sodio y azufre que la leche de
vaca (Park y col., 2007). Debido a que las cabras convierten todo el β-caroteno en vitamina A, la leche
de cabra presenta mayor cantidad de este compuesto y es mucho más blanca que la leche de vaca.
También contiene más tiamina, riboflavina, niacina, vitamina C y vitamina D que la leche de vaca (Park
y col., 2007).
36
INTRODUCCIÓN
2.2. Células somáticas
Las células somáticas están presentes en la leche de todos los mamíferos, no tienen capacidad para multiplicarse y provienen del propio animal. Según su origen, se clasifican en dos grandes
grupos: células de origen sanguíneo y células epiteliales. Normalmente estas células se encuentran
en la glándula mamaria sana, aunque puede considerarse un indicador de inflamación y/o infección
debido a que en estas situaciones se produce un incremento en el trasvase de leucocitos a la leche
(Das y Singh, 2000).
En muchos países se han establecido unos criterios de calidad para la leche de acuerdo a
los requerimientos higiénicos, tecnológicos y sensoriales. Estos criterios forman parte de un sistema
de pago que asegura la calidad de los productos finales. En los Estados Unidos, el límite legal en el
recuento de células somáticas (RCS) establecido en leche de cabra por la FDA (Food and Drug Administration) es de 1 millón de células/ml. Sin embargo en la Unión Europea no hay límite para la leche
de cabras y ovejas, como está dispuesto en los diferentes reglamentos, que establecen los criterios
generales y específicos de higiene que deben cumplir los productos alimenticios (Paape y col., 2007).
Algunos autores (Paape y col., 2007; Raynal-Ljutovac y col., 2007) han informado que los cabreros de Estados Unidos tienen dificultades para mantener el RCS en la leche de tanque por debajo
del límite establecido. Como consecuencia, muchas granjas eliminan la leche que excede el límite, lo
cual provoca importantes pérdidas económicas para el sector.
El alto RCS puede ser causado por infección pero también por razones fisiológicas. En las
ubres sanas de cabras, el RCS se incrementa progresivamente con la edad (Salama y col., 2003), durante la lactación (Gomes y col., 2006), además de fluctuaciones de un día para otro (Zeng y col., 1997),
en la que intervienen factores como el celo (Mehdid y col., 2013) y el estrés (McDougall y col., 2002).
Por tanto, la aplicación de un criterio para la evaluación de la calidad de la leche y para la detección
de mastitis está sin resolver.
En España ya hay algunas industrias queseras que están pagando la leche de cabra a los ganaderos según su composición química básica (grasa y proteína) así como en función de la calidad
higiénico-sanitaria (microbiología, RCS), pudiendo aplicarse primas o penalizaciones, tal como se
recoge en la homologación de contrato-tipo de suministro de leche de cabra con destino a su transformación en productos lácteos (Orden ARM/2387/2010, de 1 de Septiembre).
37
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
3. Factores que afectan al rendimiento y composición de la leche
La cantidad de leche producida por una cabra y su composición tienen variaciones como
consecuencia de un gran número de factores. Estos pueden actuar aisladamente oIntroducción
en combinación.
Clásicamente, los mencionados factores se han dividido en dos grupos, uno de carácter intrínseco,
Factores
intrínsecos
atribuido3.1.
al animal,
y otro
de carácter extrínseco, debido a las condiciones y circunstancias externas
que actúan sobre él.
3.1.1. Raza e individuo
La producción lechera caprina está condicionada por factores genéticos que
3.1. Factores
intrínsecos
influyen tanto sobre la cantidad (Figura 14) como en la calidad de la leche producida.
3.1.1. Raza e individuo
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38 más difundidas en el mundo tienen su
Las cabras de alta producción lechera
origen o se han seleccionado esencialmente en tres países: Suiza (Saanen y
Toggenburg), Francia (Alpina) e Inglaterra (Anglonubia). Sobre estos animales se han
INTRODUCCIÓN
Las cabras de alta producción lechera más difundidas en el mundo tienen su origen o se
han seleccionado esencialmente en tres países: Suiza (Saanen y Toggenburg), Francia (Alpina) e
Inglaterra (Anglonubia). Sobre estos animales se han realizado una gran cantidad de estudios que
abarcan la mayoría de los aspectos relacionados con los individuos y su explotación, destacando
aquellos dedicados a la producción lechera (Brito y col., 2011; Garcia-Peniche y col., 2012). En los
países, cuyas razas nativas son muy poco productivas, suele ser frecuente el cruzamiento con razas
mejoradas (Kume y col., 2012; Sanogo y col., 2012). La discutible finalidad de estos cruzamientos es la
de conservar las cualidades de rusticidad y adaptación al medio de las razas nativas pero mejorando
la producción lechera y alargando el tiempo de lactación.
La composición química de la leche también presenta grandes variaciones según la raza,
ligadas al nivel de producción de leche. En este sentido, Garcia-Peniche y col. (2012) examinaron la
composición de la leche en varias razas de alta producción durante 3 periodos (de 1976 a 1984, de
1985 a 1994, y de 1995 a 2005), y observaron incrementos en el porcentaje de proteína, el cual fue variable según las razas (7,4% en Toggenburg; 7,1% en Alpina; 6,5% en LaMancha; 5,6% en Anglonubia;
3,4% en Saanen). Sin embargo, sólo encontraron incrementos en el porcentaje de grasa en una raza
(2,1% en Anglonubia).
El estudio detallado de las variantes genéticas de la caseína as1 (Ambrosoli y col., 1988; Jordana y col., 1996) permitió realizar una nueva clasificación de las razas caprinas en función de sus
frecuencias alélicas. Cabe destacar que la concentración de as1 se correlaciona positivamente con
las propiedades de coagulación de la leche, y que nuevos trabajos genéticos están enfocados en la
mejora de esta variable (Maga y col., 2009).
Así como existe variabilidad entre razas en cuanto a producción y calidad de la leche, también
existen variaciones entre animales de la misma raza, pudiendo incluso superar estas variaciones a
las interraciales.
3.1.2. Estado y duración de la lactación
La producción de leche no es constante a lo largo de toda la lactación. De manera general la
producción aumenta hasta alcanzar el máximo pico de producción, luego desciende a medida que
avanza la lactación. El aumento de la producción de leche hasta el pico de lactación parece ser debido a una mayor capacidad de síntesis de las células epiteliales mamarias, en lugar de un incremento
39
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
en el número de células secretoras (Capuco y col., 2001; Salama, 2005). Posteriormente, el descenso
progresivo de la producción de leche, tras alcanzar el máximo, es asociado con una reducción en el
contenido de ADN total del parénquima mamario, implicando una disminución en el número de células secretoras (Knight y Peaker, 1984; Capuco y col., 2001).
La mayoría de las cabras sitúan su máxima producción entre la 3ª y 8ª semana de lactación
(Salama, 2005). Así, se han obtenido valores de pico de lactación de 2,42 kg a los 45 días (León y col.,
2012) en cabras Murciano-Granadina, de 2,48 kg a los 45 días en cabras Tinerfeñas (Capote y col.,
2000), o de 2,54 kg a los 54 días en cruce de Toggenburg con razas locales de México (Montaldo y col.,
1997). De acuerdo al Departamento de Agricultura de Estados Unidos, los máximos valores de producción alcanzados para cabras multíparas son de 4,63 kg a los 50 días en Saanen, 4,49 kg a los 40 días
en Alpina, y de 3,67 kg a los 45 días en Oberhasli (Animal Improvement Programs Laboratory, 2004).
En lo que respecta a la composición, el contenido de grasa sigue una evolución opuesta
a la evolución de la producción de leche, es decir, una rápida disminución en el transcurso de las
primeras semanas de lactación, a la que sigue un mínimo que se alcanza aproximadamente entre el
final del 2º y el 6º mes de lactación, y posteriormente, un aumento lento y progresivo (Peris, 1994). Sin
embargo, algunos autores no consiguieron observar diferencias de este componente entre las fases
de lactación temprana, media o tardía (Capote y col., 2008). En cuanto a la proteína, la mayoría de los
autores encontraron que permanece casi constante con pequeñas fluctuaciones alrededor de un
valor medio (Peris, 1994; Hejtmankova y col., 2012). Finalmente, la evolución de la lactosa presenta
un comportamiento inverso al de la grasa, es decir aumentando en la primera parte de la lactación y
disminuyendo en la última (Park y col., 2007).
3.1.3. Edad y número de lactación
Parece claro que la producción de leche es menor en cabras primíparas que en cabras multíparas (Goetsch y col., 2011). De hecho, las únicas diferencias significativas se han observado entre la
primera y el resto de las lactaciones (Zeng y Escobar, 1995). Ello puede deberse a que entre la primera
y segunda lactación los animales manifiestan una importante diferencia en el desarrollo corporal,
más acentuada en cabras que se cubren precozmente de forma sistemática, como ocurre en las Islas
Canarias (Capote y col., 2000), Por tanto, las cabras en primera lactación tienen menor volumen de
ubre (Salama y col., 2004) y por tanto una menor cantidad de leche secretada por unidad de volumen
40
INTRODUCCIÓN
en comparación con las cabras multíparas (Knight y Wilde, 1993). De esta forma, Zahraddeen y col.
(2009) encontraron un incremento progresivo en el rendimiento lechero entre la 1ª y 3ª lactación en
varias razas de cabras de doble propósito (Red Sokoto, Sahel y West African Dwarf). Mientras que
Carnicella y col. (2008) y Mioc y col. (2008) encontraron un aumento en la producción de leche casi
constante desde la 1ª hasta la 4ª lactación en cabras Maltesa, Saanen y Alpina.
En cuanto a los componentes de la leche considerados de forma porcentual, algunos trabajos
recientes señalaron que las concentraciones de grasa y proteína fueron similares entre los cinco primeros partos, pero fue menor en la 6ª lactación (Zeng y col., 2008), mientras que otros estudios habían
observado previamente un incremento de la cantidad de grasa al mismo tiempo que el contenido de
proteína disminuía al aumentar el número de lactaciones (Morand-Fehr y col., 1986).
3.1.4. Prolificidad
La producción de leche de cabra puede verse influenciada por el tamaño de la camada (Figura
15). Delgado-Pertiñez y col. (2009) observaron una mayor cantidad de leche producida en cabras de
raza Payoya con dos cabritos respecto a las de uno, durante las primeras 5 semanas después del parto, con independencia de los sistemas de lactancia y de ordeño. Sin embargo a partir de la semana 6
hasta la 30, las producciones fueron similares. Por tanto, el hecho de que las cabras con más de dos
crías liberen cantidades superiores de lactógeno placentario durante la gestación, parece tener un
mayor impacto sobre la posterior producción de leche, que las diferencias producidas por la estimulación de los cabritos al lactar (Goetsch y col., 2011).
Figura 15. Cabra Majorera con una (izquierda) o dos (derecha) crías. (U.D. Producción Animal ULPGC).
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
En lo referente a la composición de la leche, algunos estudios observaron que la prolificidad
influía sobre el porcentaje de proteína, si bien no había ningún efecto sobre la grasa (Peris y col.,
1997). Sin embargo, en otros experimentos encontraron que las cabras que tenían dos cabritos, independientemente de su origen genético, presentaban una mayor concentración de grasa, proteína y
lactosa (Zygoyiannis, 1994).
3.1.5. Estado sanitario
Existen numerosos estudios que han demostrado que los procesos infecciosos en cabras provocan una disminución en la producción de leche, con un incremento en el RCS que afecta a la vida
media de la leche destinada al consumidor (Zeng y Escobar, 1995; Huijps y col., 2008). Hay que tener
en cuenta que durante la lactación ocurren cambios en el rendimiento lechero relacionados con
procesos no infecciosos, los cuales pueden resultar en un efecto de concentración de las células
somáticas (Paape y col., 2007; Goetsch y col., 2011). Por tanto, el aumento brusco del RCS al final de la
lactación donde se produce un descenso en el rendimiento lechero, puede ser resultado de una mayor transferencia de células de origen sanguíneo a la leche, debido a una mayor actividad de factores
relacionados con la involución de la glándula mamaria (Manlongat y col., 1998).
3.2. Factores extrínsecos
3.2.1. Alimentación
La alimentación del ganado caprino no sólo influye en la cantidad de leche sino también en la
calidad de la misma y por ende en la del queso (Pulina y col., 2008). Debido a la importancia de este
factor (Figura 16), son numerosos los trabajos y revisiones bibliográficas realizadas a tal efecto (Min
y col., 2005; Álvarez y col., 2007). Además, buena parte de ellos están dedicados a la búsqueda de alimentos alternativos, en general subproductos de la industria alimentaria (Azzaz y col., 2012; RomeroHuelva y col., 2012).
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INTRODUCCIÓN
Figura 16. Cabras Palmeras recibiendo una ración de concentrado durante el ordeño. (ICIA).
Entre los componentes de la leche, la grasa es el más sensible a los cambios nutricionales
del animal, siendo la fuente de forraje y los suplementos grasos los que afectan en mayor medida su
cantidad y sobre todo su calidad (Sanz Sampelayo y col., 2007). El rango de variación de la proteína
es más pequeño que el de grasa, sin embargo, parte de los estudios están enfocados en suplementos
que puedan variar el contenido de αS1-caseína (Valenti y col., 2012).
Muchas zonas de Canarias no tienen suficientes recursos para el pasturaje de los animales,
lo cual ha ocasionado que las cabras en sistemas intensivos tengan raciones más ricas en alimentos
concentrados y con menos porcentaje de fibra. Estas dietas afectan significativamente el contenido
de grasa en la leche, además de causar muchos problemas de salud en el animal (Álvarez y col.,
2007). Dicho problema no es fácil de resolver simplemente con la importación de forrajes, por los
elevados costes de transporte, que perjudicaría directamente a los cabreros.
3.2.2. Sistema de producción
Debido a que la dieta afecta la composición de la leche de cabra, los sistemas de producción
afectan directamente estos parámetros, ya que los extensivos están basados ​​en el pastoreo y ramoneo (Figura 17), mientras que los intensivos en la utilización de piensos y concentrados. Incluso,
existen diferencias dentro de los mismos sistemas productivos. Por ejemplo, cuando se compararon
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
tres sistemas de producción caprina basados en
​​ pastos naturales de llanura, colinas y montaña, la
producción de leche resultó ligeramente inferior en los pastos de montaña, pero su contenido de grasa y proteína, así como los porcentajes de ácidos grasos poliinsaturados fueron mayores respecto a
los otros dos sistemas de manejo (Morand-Fehr y col., 2007).
Figura 17. Cabras de pastoreo en la isla de La Palma. (ICIA).
El tipo de especies forrajeras y de concentrados suministrados en la alimentación, también
afecta la calidad de los quesos. Soryal y col. (2004) observaron una puntuación mayor en el sabor de
los quesos elaborados con leche de cabras que pastaban sin concentrado suplementario en comparación con aquellas que estaban confinadas y cuya dieta estaba basada en concentrados comerciales y heno de alfalfa.
En Canarias generalmente las cabras son explotadas en sistemas semi-extensivos, ya que el
pastoreo forma parte importante de la ganadería tradicional. Algunos autores han señalado que al
realizarse de forma controlada contribuye a la biodiversidad y al desarrollo sostenible de la región
(Mata y col., 2010).
3.2.3. Factores climáticos
Se ha señalado que las altas temperaturas, la incidencia de radiación solar y una humedad
elevada, son factores condicionantes sobre los animales que afectan su nivel de producción (Sila-
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nikove, 2000a). Sin embargo, estos factores no afectan de igual manera a las distintas razas, ya que
por ejemplo, las cabras de zonas templadas de Europa se ven más perjudicadas por las altas temperaturas que las cabras autóctonas de zonas cálidas de Asia, África y América del Sur (Gaughan y
col., 2009).
Por otro lado, aunque la alta producción lechera está relacionada con los recursos hídricos
disponibles en la zona (Silanikove, 2000b), cabe destacar que las cabras están mejor adaptadas
que las vacas y ovejas a los largos períodos de sequía y a las zonas áridas (Figura 18), llegando
incluso a producir 2 litros de leche al día con restricción de agua si se alimentan adecuadamente
(Maltz y col., 1982).
Figura 18. Cabras de raza Majorera en la isla de Fuerteventura. (ICIA).
3.2.4. Condiciones de ordeño
Aunque el ordeño mecánico está bastante generalizado en los países industrializados, aún
existen muchas regiones donde el ordeño manual es frecuente. Existen pocos trabajos que comparen
la producción y composición de la leche entre ambos métodos de ordeño. Aunque la estimulación
manual mejora el vaciado de la ubre respecto al ordeño a máquina, no debería haber diferencias en
cuanto a la producción siempre y cuando ambos métodos se realicen adecuadamente (Bruckmaier
y Blum, 1998). En lo referente al RCS, algunos autores no han conseguido diferencias significativas
entre el ordeño manual y el mecánico, aunque si un mayor recuento de bacterias en la leche del orde-
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
ño manual (Zeng y Escobar, 1996). Sin embargo, otros afirman que existe una importante variabilidad
en el RCS, en lo referente al método de ordeño utilizado, con mayores recuentos durante el ordeño
manual (Haenlein, 2002).
Por otro lado, los parámetros y ajustes en la máquina de ordeño influyen considerablemente
sobre la extracción de leche, tanto en términos de cantidad como de calidad. Así por ejemplo, se ha
reportado que las condiciones óptimas de ordeño en cabras griegas se dan con una frecuencia de
pulsación de 70-90 pulsos/min, una presión de succión entre 36-44 kPa y una relación de pulsación de
65:35 (Sinapis y col., 2000). En razas Alpina y Saanen, una alta frecuencia en la ordeñadora (90 y 120
pulsos/min y una relación de pulsación de 60:40) reduce el tiempo de ordeño, mientras que la baja frecuencia (60 pulsos/min y una relación de pulsación de 50:50) alarga el tiempo de ordeño y disminuye
el flujo de leche (Billon y col., 2005). Además, si el nivel de vacío es muy alto, se produce un estrangulamiento de los pezones en las pezoneras disminuyendo el caudal de leche extraída y puede incidir
en la aparición de mastitis, pero si el vacío es muy bajo, es muy frecuente la caída de las pezoneras
ya que no succionan adecuadamente a los pezones de las cabras y por tanto retrasa el tiempo de
ordeño (Marnet y McKusick, 2001).
Cuando empezaron a implantarse las maquinarias de ordeño en las Islas Canarias, los ganaderos se quejaban de que esta práctica producía mastitis a las cabras. Sin embargo, las razones
principales eran que no se manejaban unas adecuadas condiciones higiénicas, además de que las
marcas proveedoras no se habían adaptado a las necesidades de esta especie, tanto en parámetros
como en materiales. Hoy en día los ganaderos conocen la importancia de la máquina de ordeño, representado un grave problema si ésta sufre algún desperfecto o daño (Capote y col., 2010).
En lo referente a la frecuencia de ordeño, en países como Francia, Suiza y Alemania que cuentan con una explotación caprina tecnificada, es habitual realizar dos ordeños al día, cuya eficacia
está respaldada por numerosos estudios que otorgan un elevado incremento de las producciones lecheras. Así, en razas como Alpina y Saanen, las diferencias a favor del doble ordeño oscilaban entre
un 26 y 45% (Mocquot y Auran, 1974; Wilde y Knight, 1990), aunque en trabajos más recientes dichas
diferencias están alrededor del 16% (Komara y col., 2009).
La totalidad de las ganaderías caprinas del Archipiélago Canario realizan un solo ordeño diario. Este hábito se vio favorecido por la costumbre de elaborar el queso justo después de haber ordeñado, debido a la imposibilidad de conservar la leche, lo cual implicaba una tarea exigente y difícil
de realizar dos veces al día, y más si consideramos las grandes distancias que recorrían los cabreros
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INTRODUCCIÓN
en la búsqueda de zonas de pastoreo. Sin embargo, las mejoras tecnológicas producidas en el sector
caprino en los últimos años con la proliferación de maquinaria de ordeño, tanques de refrigeración e
industrias con circuito de recogida de la leche, suponía que la variación en la frecuencia de ordeño
permitiría aumentar los rendimientos de los rebaños, pero los primeros estudios realizados en cabras
Tinerfeñas consiguieron incrementos entre sólo el 6 y 8% (Capote y col., 2000).
4. Estructura anatómica y conformación de la glándula mamaria
4.1. Anatomía de la glándula mamaria caprina
La ubre caprina, conformada por dos glándulas independientes, está situada en la región
inguinal cubriendo la cara interna de los muslos y con una proyección desde atrás hacia adelante.
Cada glándula mamaria está compuesta por una cisterna y una papila o pezón, y se separa de la
otra por un surco intermamario. En las cabras, al igual que en el resto de las hembras con aptitud
lechera, el desarrollo mamario constituye la base donde podrá proliferar el tejido secretor (Knight
y Peaker, 1982).
Cada complejo mamario se compone de diversos elementos funcionales responsables del
proceso biosintético, almacenamiento y transporte de la leche (Figura 19):
Figura 19. Vista lateral glándula mamaria caprina. A: parénquima mamario; b: porción cisternal del seno lactífero; c: porción papilar del seno lactífero; d: papila mamaria; e: nódulos linfáticos mamarios; f: conducto y orificio papilar; g: conductos lactíferos colectores. (Sandoval, 2003).
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
4.1.1. Parénquima glandular
En el parénquima glandular o tejido noble se encuentran las unidades secretoras, o alvéolos,
que presentan como característica primordial la presencia de un epitelio secretor que delimita internamente el lumen donde se deposita la leche secretada por la células. Exteriormente cada alvéolo
presenta una compleja red de capilares arteriales y venosos que están en íntimo y estrecho contacto
con el epitelio basal (Constantinescu y Constantinescu, 2010). Los alvéolos agrupados en racimos,
lobulillos y lóbulos, son vaciados por pequeños canalículos que confluyen para formar conductos de
mayor tamaño, llamados canales galactóforos, los que a su vez convergen en estructuras de mayor
diámetro interno, con límites más difusos denominados cisternas de la mama (Ferrando y Boza, 1990).
Finalmente este sistema de conducción se comunica con una cisterna del pezón, ubicada en
este último y cuyo volumen varía según el tamaño del pezón. El interior de la papila mamaria presenta
una mucosa muy plegada para evitar el flujo espontáneo de leche al exterior así como la penetración
de agentes patógenos, y una concentración de fibras musculares que contienen numerosas terminaciones nerviosas y vasos sanguíneos (Suárez-Trujillo y col., 2013).
Otro elemento anatómico funcional de importancia lo constituyen las células mioepiteliales
que envuelven externamente a los alveolos y que por ser fibras musculares lisas responden activamente a las descargas de oxitocina, permitiendo un correcto vaciamiento de la leche acumulada en
las estructuras no cisternales (Bruckmaier y Blum, 1998).
4.1.2. Sistema suspensorio
El aparato suspensorio de la ubre lo conforma una red de fibras de naturaleza elástica y fibrosa, procedentes de la pared ventral del abdomen, que penetran en el parénquima mamario a diferentes niveles, evitando que los cuerpos glandulares graviten directamente sobre la piel que los
envuelve (Suárez-Trujillo y col., 2013). La proporción de tejido glandular y de tejido de sostén presenta
una buena caracterización de una glándula mamaria en cuanto a su mayor o menor capacidad productiva. Así una glándula con una gran cantidad de tejido de sostén presentará un aspecto exterior
con escasa variación antes o después del ordeño, mientras que una glándula rica en tejido noble
presentará un aspecto muy retraído después del ordeño (Ferrando y Boza, 1990).
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4.1.3. Sistema circulatorio y linfático
Para poder sintetizar la leche, debe circular por la ubre una enorme cantidad de sangre, ya
que se requiere una elevada proporción de nutrientes para que las células secretoras la produzcan.
Así mismo, las células alveolares requieren tiempo para la captura de estos nutrientes, por lo que un
paso de sangre a alta velocidad no resolvería el problema. Para que la secreción láctea se lleve a
cabo eficientemente, el aporte sanguíneo se ralentiza a nivel alveolar como consecuencia del enorme desarrollo del sistema venoso de la ubre, encontrándose alrededor de las mamas, ricas redes
capilares conectadas con amplios plexos venosos por los que la sangre circula muy lentamente (Ferrando y Boza, 1990).
También cabe destacar la existencia de una gran representación linfática, destacando los
ganglios linfáticos mamarios que actúan como linfocentros, y que desempeñan un importante papel
como barrera defensiva frente a las infecciones que puedan afectar a la ubre (Constantinescu y
Constantinescu, 2010).
4.2. Morfología de la ubre de las razas canarias
La morfología de la ubre es un importante parámetro en la ganadería caprina por su contribución en la producción de leche y la aptitud de ésta para el ordeño mecanizado. Los parámetros más
utilizados en la definición de la morfología de la ubre son: profundidad y volumen de la ubre, morfología del pezón (longitud, anchura, ángulo de implantación y situación antero-posterior), y altura de las
cisternas mamarias (Figura 20).
Una morfología de ubre adecuada es muy importante para una buena adaptación del animal
a la máquina de ordeño, ya que puede evitar algunos efectos indeseables, como por ejemplo la inhibición del reflejo de eyección láctea, o la caída de pezoneras que conllevaría un mayor tiempo de
ordeño (Barillet, 2007). Peris (1994) al estudiar la aptitud al ordeño mecánico de cabras MurcianoGranadina, describió que existe una gran heterogeneidad en los criterios metodológicos y las medidas morfológicas evaluadas, así como en el estado de lactación utilizado por cada autor para evaluar
la aptitud al ordeño.
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Figura 20. Medidas morfológica de la ubre. DEP: distancia entre pezones; ACS: altura cisterna-suelo; APS: altura pezónsuelo; AIUS: altura inserción-suelo; PU: profundidad ubre. (U.D. Producción Animal ULPGC).
La morfología de la ubre ha sido descrita en las principales razas lecheras: Saanen y Alpina
(Manfredi y col., 2001), Toggenburg (Wang, 1989), Murciano-Granadina (Peris y col., 1999). En los trabajos se describen distintas formas de ubres: redondeadas o globosas, ovales, piriformes, pendulares
o planas. También diferentes tipos de pezón: cónicos, cilíndricos, en forma de botella o bulbosos,
pequeños, o voluminosos. En el caso de la razas canarias, la ubre se caracteriza porque la altura del
pezón es mayor que la altura del fondo de cisterna en un gran número de animales (Figura 21), una
circunstancia negativa en el momento del ordeño, ya que es necesaria la intervención manual para
levantar la ubre y extraer la porción de leche que hay debajo del pezón, lo cual incrementa el tiempo
de ordeño (Capote y col., 2008).
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Figura 21. Típica ubre de las cabras canarias. (U.D. Producción Animal ULPGC).
Algunos autores han señalado que la selección genética para mejorar la producción lechera
llevada a cabo en las últimas décadas, ha producido efectos indeseables en la morfología mamaria,
como la tendencia de que las ubres tengan ubicados los pezones más horizontalmente para incrementar la capacidad cisternal pero que trae como consecuencia una menor ordeñabilidad de los
animales (Marnet y McKusick, 2001; Barillet, 2007).
5. Fisiología de ordeño
El inicio masivo de la secreción láctea corresponde al momento del parto en que se produce
un cambio hormonal importante, con el descenso en el nivel de la progesterona y un incremento de
estrógenos, prolactina, y glucocorticoides (Davis y col., 1979). La lactogénesis comprende la síntesis
intracelular de la leche y su posterior transferencia desde el citoplasma hacia el lumen alveolar. El
componente de base del tejido secretor es el alvéolo, envuelto por una capa de células mioepiteliales
que ayudan en la contracción de los alvéolos por efecto de la oxitocina, produciendo la expulsión de
la leche hacia los conductos galactóforos. Este proceso neurohormonal es provocado por estímulos
como el amamantamiento de la cría o el proceso de ordeño (Park y Haenlein, 2010).
Las terminaciones nerviosas del pezón están conectadas con el sistema nervioso central y
el hipotálamo a través de las raíces dorsales de los nervios lumbares de la médula espinal. Cuando
un estímulo alcanza el sistema nervioso central provoca que el lóbulo posterior de la hipófisis libere
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
oxitocina. La oxitocina viaja a través del flujo de sangre hasta la glándula mamaria, donde causa la
contracción de las células mioepiteliales (Figura 22) (Bruckmaier y Blum, 1998).
Figura 22. Esquema de eyección de leche en cabras. (Caja, 2003).
5.1. Efectos de la oxitocina sobre la eyección de leche
La oxitocina es un neuropéptido responsable de la eyección de la leche, con el consecuente
vaciado de la ubre. Dependiendo del grado de estimulación de la glándula mamaria, se producen
diferentes respuestas en la liberación de oxitocina. De esta forma, el amamantamiento de la cría es
un estímulo más potente que el ordeño, mientras que el ordeño manual induce una liberación más
pronunciada de oxitocina que el ordeño a máquina (Bruckmaier y Blum, 1998). Además, la estimulación previa al ordeño es importante en algunas especies como el ganado bovino porque aumenta
los niveles de oxitocina y promueve la inducción temprana de eyección de la leche para evitar una
interrupción del flujo de leche durante el ordeño, sin embargo en cabras no es tan importante esta
estimulación previa por el gran volumen de leche almacenado en la cisterna, y que está disponible en
el momento del ordeño (Bruckmaier y Wellnitz, 2008).
El proceso de eyección de leche en cabras, en respuesta a la oxitocina, es similar al de vacas
y ovejas, pero la extracción de la leche es diferente debido a la morfología de la ubre (Bruckmaier y
Blum, 1998). En cabras, la liberación de oxitocina es altamente variable en el mismo animal y entre
diferentes individuos de la misma raza, siendo fácilmente inducida por estimulación táctil previa o por
la máquina de ordeño (Bruckmaier y Blum, 1998; Marnet y McKusick, 2001).
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5.2. Efectos de la administración de oxitocina exógena sobre la producción de leche
Aunque existen numerosos informes de que la administración exógena de oxitocina en el momento del ordeño puede aumentar la producción de leche, hay contradicciones en la literatura con
respecto a sus efectos sobre el rendimiento lechero y calidad de la leche. Éstos se deben principalmente a diferencias en la metodología y diseño experimental, que van desde el número de animales
utilizados, estado de lactación, inyección seguida de remoción de leche o no, inyección administrada
con las ubres llenas o vacías, y dosis de oxitocina administrada (Lollivier y col., 2002).
La administración de dosis intravenosas entre 0,1 y 1 UI de oxitocina puede inducir la bajada de
la leche en cabras, ya que sólo es necesario rebasar un umbral mínimo de concentración de oxitocina
para iniciar el proceso (Schams y col., 1984). Sin embargo, en la mayoría de los trabajos experimentales,
los investigadores han utilizado dosis con cantidades suprafisiológicas (Lollivier y col., 2002).
En vacas, se ha reportado que la administración exógena de oxitocina es una terapia eficaz
contra la mastitis (Macuhova y col., 2004). Sin embargo no se han encontrado cambios aparentes en
el sistema inmune por los tratamientos con oxitocina, aunque las inyecciones en cantidades suprafisiológicas pueden ayudar en la eliminación de microorganismos patógenos debido a un completo
vaciado de la ubre (Werner-Misof y col., 2007). Adicionalmente, algunos estudios confirman una reducción en la eyección espontanea de leche después de retirar los tratamientos crónicos de oxitocina, lo cual puede deberse a una disminución de la oxitocina liberada desde la hipófisis, o por una
reducción en la contractibilidad de las células mioepiteliales a niveles fisiológicos de oxitocina en
sangre (Bruckmaier, 2003).
6. Fraccionamiento lechero
En el instante del ordeño, se considera que la leche se encuentra almacenada en la ubre en
dos niveles bien diferenciados (fracciones de ubre), o como se obtiene durante una rutina de ordeño
completa (fracciones de ordeño).
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
6.1. Fracciones de ubre
6.1.1. Leche cisternal
Cierta cantidad de leche está contenida en la cisterna o seno glandular. La especial estructuración anatómica de la glándula mamaria del caprino, que incluye la presencia de grandes
cisternas (Figura 23), permite que buena parte del contenido de leche almacenada en el interior de
la glándula pueda ser evacuada en forma pasiva, es decir, sin un proceso de contracción (Bruckmaier y Blum, 1998).
Figura 23. La ubre caprina canaria destaca por sus grandes cisternas. (U.D. Producción Animal ULPGC).
6.1.2. Leche alveolar
Una parte de la leche se acumula en los alvéolos y en la red de canales y conductos (Figura 24), y está fijada por fuerzas capilares. Para su obtención se precisa de la participación activa
del animal, a través de la puesta en marcha del mecanismo de eyección de leche (Bruckmaier y
Wellnitz, 2008).
54
INTRODUCCIÓN
Figura 24. Representación de la expulsión de la leche contenida en los alveolos. (Schmidt, 1971).
El reparto entre la leche cisternal y alveolar se determinaba mediante el uso de una cánula que
se introducía por el esfínter del pezón y permitía el drenaje de la leche cisternal (Peaker y Blatchford,
1988). No obstante, esta técnica puede sobreestimar el volumen de leche cisternal, ya que algunas
razas son muy sensibles a la liberación espontánea de oxitocina endógena, como consecuencia de
reflejos condicionados al ordeño o como resultado de la manipulación del pezón. Por ello, las nuevas
técnicas incluyen el uso de un antagonista de los receptores de oxitocina para bloquear la eyección
espontánea de leche (Wellnitz y col., 1999).
6.2. Fracciones de ordeño
6.2.1. Leche de máquina
El fraccionamiento obtenido durante el ordeño mecánico permite diferenciar una porción de
leche recogida desde la colocación de las pezoneras hasta el cese de flujo de leche sin intervención
alguna por parte del ordeñador (Figura 25).
6.2.2. Leche de apurado a máquina
La morfología de ubre de muchas razas caprinas hace necesario realizar un masaje de las
regiones cisternales y alzar el ligamento suspensorio por parte del ordeñador, antes de la retirada de
las pezoneras, para favorecer la remoción de la leche contenida debajo de los pezones (Figura 25).
55
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
6.2.3. Leche residual
La leche total contenida en la glándula mamaria difícilmente se puede extraer en su totalidad
por medios mecánicos o manuales, puesto que una parte sólo puede ser extraída por mecanismos
hormonales. Así pues, mediante una inyección de oxitocina se extrae la fracción retenida en el tejido
mamario, y aunque no se considera propiamente como una fracción de ordeño, permite expresar el
grado de vaciado de la ubre conseguido por medio del ordeño mecánico.
Figura 25. Fracción de leche de máquina (izquierda) y de apurado a máquina (derecha). (ICIA).
Por consiguiente, las cabras con mejor adaptación a la máquina de ordeño serán aquellas que
presenten una mayor cantidad de leche de máquina, y menor volumen de leche de apurado y residual,
lo que implica una reducción en el tiempo dedicado al ordeño. Sin embargo, en las explotaciones
ganaderas, hay una tendencia centrada en reducir el número de operaciones durante el ordeño, omitiendo el apurado a máquina (McKusick y col., 2003).
Por otro lado, se ha señalado la importancia de la morfología de ubre sobre las fracciones de
ordeño, destacando la red canalicular, la altura de las cisternas mamarias y el ángulo de inclinación
de los pezones (Le Du, 1985), habiéndose resaltado también que las ubres globosas son más fáciles
de ordeñar que las ubres descendidas (Capote y col., 2006). Además, la frecuencia de ordeño afecta
especialmente la fracción de apurado a máquina, donde el doble ordeño incrementa significativa-
56
INTRODUCCIÓN
mente los porcentajes en las cabras Tinerfeñas, debido al hecho de tener que realizar esta labor dos
veces para un correcto vaciado de la ubre (Capote y col., 2009).
De forma general, los valores de reparto de leche durante el ordeño en caprino se sitúan entre 61 a 90% para leche de máquina, 10 a 23% para leche de apurado a máquina y un 10 a 17% para
la leche residual (Capote y col., 2000). Por otra parte, la fracción de leche de máquina es la que más
disminuye a lo largo de la lactación, siguiendo una evolución paralela a la leche total ordeñada, e
inversa al de la leche de apurado a máquina, en donde la leche residual permanece más o menos estable, pero existiendo una alta variabilidad entre individuos (Peaker y Blatchford, 1988; Capote y col.,
2008). Díaz y col (2013) estudiaron los niveles de cortisol sobre el fraccionamiento lechero en cabras
Murciano-Granadina y no encontraron correlación entre éstos con el volumen de leche de apurado a
máquina y el tiempo total de ordeño, por lo que las variaciones de esta hormona pueden estar asociadas a factores fisiológicos en el animal y no necesariamente al estrés. En general, estas fracciones
tienden a mantener un volumen constante a medida que los animales se adaptan a la máquina de
ordeño (Rovai, 2001).
57
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67
ARTÍCULO 1
ARTÍCULO 1
J. Dairy Sci. 96:1071–1074
http://dx.doi.org/10.3168/jds.2012-5435
© American Dairy Science Association®, 2013.
Short communication: Effects of milking frequency on udder
morphology, milk partitioning, and milk quality in 3 dairy goat breeds
A. Torres,* N. Castro,† L. E. Hernández-Castellano,† A. Argüello,†1 and J. Capote*
*Instituto Canario de Investigaciones Agrarias, La Laguna, Tenerife 38200, Spain
†Department of Animal Science, Universidad de Las Palmas de Gran Canaria, 35413 Arucas, Spain
ABSTRACT
use of an oxytocin receptor antagonist to block spontaneous milk ejection (Wellnitz et al., 1999), allowing
a reliable separation between both fractions. This is
important because the udder morphology of some dairy
goat breeds (e.g., Tinerfeña breed) is characterized
by higher teat-floor distance (TF) than cistern-floor
distance (CF), a negative circumstance that makes
more difficult the emptying of cisternal milk by gravity
(López et al., 1999).
The aim of the present study was to determine the
effects of milking frequency on udder morphology, milk
partitioning, composition of each fraction, and SCC of 3
dairy goat breeds (Majorera, Tinerfeña, and Palmera).
The present study was performed on the experimental
farm of the Instituto Canario de Investigaciones Agrarias in Tenerife (Spain) on 36 dairy goats belonging to
3 different breeds: Majorera (n = 12), Tinerfeña (n =
12), and Palmera (n = 12). The experimental animal
procedures were approved by the Ethical Committee of
the Universidad de Las Palmas de Gran Canaria (Arucas, Spain). Goats with symmetrical udder halves were
in third parity with 124 ± 8 DIM at the beginning of
the experiment. The milking frequency before the start
of the experimental period was once per day. During
a 5-wk period, each goat was milked once daily in the
left mammary gland (×1; at 0700 h), whereas the right
mammary gland was milked twice daily (×2; at 0700
and 1700 h). The animals were fed with commercial
concentrate, maize, lucerne, wheat straw, and a vitamin-mineral corrector in accordance with the guidelines
issued for lactating goats by Institut National de la
Recherche Agronomique (INRA, Paris, France; Jarrige,
1990). Goats were milked in a double 12-stall parallel
milking parlor (Alfa Laval Iberia SA, Madrid, Spain)
equipped with recording jars (4 L ± 5%) and a low-line
milk pipeline. Milking was performed at a vacuum pressure of 42 kPa, a pulsation rate of 90 pulses/min, and
a pulsation ratio of 60/40, in accordance with Capote
et al. (2006). The milking routine included wiping dirt
off teat ends and stripping 2 to 3 squirts of milk from
each teat; machine milking and stripping milking, done
by the operator to remove the milk remaining in the
udder before cluster removal; and teat dipping in an
Thirty-six dairy goats of 3 breeds (Majorera, Tinerfeña, and Palmera) in mid lactation (124 ± 8 d in milk)
were subjected unilaterally to once (×1) or twice daily
milking (×2) for 5 wk to evaluate udder morphology,
milk partitioning, and somatic cell count. Majorera and
Palmera goats presented the highest and lowest udder
depth values, respectively, whereas the differences between initial and final cistern-floor and teat-floor distances were not affected by milking frequency or breed
factors. Cisternal and alveolar milk percentages were
similar between ×1 and ×2 in the studied breeds. Milking frequency did not affect milk composition in the
cisternal fraction, suggesting a greater transfer of milk
from the alveoli to the cistern during early udder filling.
However, milking frequency caused diverse changes in
the milk composition in the alveolar fraction, especially
in fat, lactose, and total solids contents. No udder halves
presented clinical mastitis during the experimental period, suggesting that ×1 does not impair udder health
and indicating that the studied breeds are adapted to
this milking frequency.
Key words: milking frequency, milk partitioning,
milk quality, dairy goat
Short Communication
Intramammary filling rate and cisternal capacity to
store milk determine the choice of an adequate milking
routine. Overfilling of the udder increases intramammary pressure and distention of the alveoli, which can
compromise subsequent milk synthesis as has been
reported by Peaker (1980). Animals with large cisterns
are milked faster with simplified routines and are better
at tolerating extended milking intervals (Knight and
Dewhurst, 1994; Ayadi et al., 2003; Salama et al., 2003).
Techniques for determining cisternal and alveolar
milk fractions have been improved and include the
Received February 15, 2012.
Accepted October 26, 2012.
1
Corresponding author: [email protected]
1071
71
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
1072
TORRES ET AL.
iodine solution (P3-cide plus; Henkel Hygiene, Barcelona, Spain).
Milk recording and sampling were done at wk 1, 3,
and 5. Before the experiment, the goats were exposed
to 3 wk of adaptation. In the first and second weeks,
the goats began to enter the milking parlor in the afternoon, but the goats were not milked. During the
third week of adaptation, the goats were milked once
and twice daily in the left and right mammary gland,
respectively, but the milk was not collected. Udder
measurements of each goat were taken just before the
first and the last milking of the experimental period.
The following udder measurements were performed:
CF and TF, recorded as the differences between initial
and final measurements (ΔCF and ΔTF), and udder depth (UD), recorded as the difference in distance
between the udder floor and the cistern floor.
Before the a.m. milking (24- and 14-h milking intervals for ×1 and ×2, respectively) on the sampling days,
each goat was injected intravenously with 0.8 mg of an
oxytocin receptor blocking agent (Tractocile; Ferring
SAU, Madrid, Spain) inside a pen immediately before
entering the parlor to record cisternal milk volume.
After cisternal milk removal, the goats were injected
intravenously with 2 IU of oxytocin (Oxiton; Laboratorios Ovejero, León, Spain) to reestablish milk ejection
to allow the measurement of alveolar milk. Cisternal
and alveolar milk volumes were recorded by using the
recording jars in the milking parlor and milk samples
were collected separately for each udder half and fraction.
Milk samples (cisternal and alveolar fractions) were
analyzed immediately after collection to determine milk
composition and SCC. Protein, fat, lactose, TS, and
SNF percentages were determined using a MilkoScan
133 analyzer (Foss Electric A/S, Hillerød, Denmark),
and SCC using a Fossomatic 90 cell counter (Foss
Electric A/S). Somatic cell count was calculated by a
weighted average of the cisternal and alveolar SCC.
The statistical analysis used to evaluate the effects of
breed and milking frequency on morphological parameters of udder, milk partitioning and SCC was PROC
MIXED of SAS (version 9.0; SAS Institute Inc., Cary,
NC). The model included fixed effects of milking frequency (×1 or ×2) and breed (Majorera, Tinerfeña, or
Palmera) and their interactions. The repeated statement was used to take into account repeated measures
for each individual animal. Differences among the
breeds and milking frequencies were evaluated using a
multiple comparison test following the Tukey-Kramer
method. Statistical differences were considered significant at P < 0.05. Data are presented as least squares
means.
The ΔCF and ΔTF (Table 1) did not differ due to
milking frequency or breed (P > 0.05). Knight and
Dewhurst (1994) found that large cisternal size may
explain the small negative effects of longer milking
intervals on udder morphology because it is better prepared to accommodate greater milk accumulation, and
may explain the absence of differences in the cistern
descent of goat udders.
Majorera and Palmera goats presented the highest
and lowest UD values, respectively (Table 1). The increase in UD values during the experimental period can
be explained because ΔTF were lower than ΔCF, which
implies that increasing the cistern depth increases the
UD. The cistern depth is a consequence of teat placement of the studied goats whose teats are not located in
the ventral portion of the udder (Capote et al., 2006).
Cisternal and alveolar milk percentages were similar
between ×1 (24 h after milking) and ×2 (14 h after
milking) in Majorera, Tinerfeña, and Palmera breeds
(Table 1). Salama et al. (2004) did not find differences
in cisternal milk fraction in Murciano-Granadina goats
between ×1 and ×2 when milking intervals were 16 and
24 h (values ranged from 66 to 76%). The differences
observed in the cisternal and alveolar fractions between
breeds may be explained by the cisternal size, because
greater cisterns are able to store more milk. Bruckmaier
et al. (1997) explained that a large absolute cisternal
volume implies that a large fraction of the milk is stored
within the cisternal cavities and it varies according to
breed.
Percentages of cisternal milk components (Table 1)
were not affected by milking frequency (P > 0.05). This
absence of differences between ×1 and ×2 goats might
be due to the fact that approximately 80% of total milk
was stored in the cisternal compartment and most of
the transfer of milk from the alveoli and small milk
ducts had already taken place. However, McKusick
et al. (2002) observed marked differences in milk fat
percentage in the cisternal fraction between different
milking intervals in dairy ewes, in which the cistern was
only capable of storing approximately 50% of the total
milk volume, being more susceptible to changes in the
transfer of milk components.
Alveolar milk of ×1 goats contained higher percentages of fat and TS than alveolar milk of ×2 goats, but
these differences were significant only in the Majorera
breed. McKusick et al. (2002) explained that a transfer
of milk fat from the alveoli to the cistern occurs during early udder filling; however, this transfer no longer
takes place during later intervals, resulting in an accumulation of milk fat in the alveolar compartment.
Alveolar milk was richer in fat content than cisternal
milk in all breeds and milking intervals, which agrees
Journal of Dairy Science Vol. 96 No. 2, 2013
72
ARTÍCULO 1
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SHORT COMMUNICATION: UNILATERAL MILKING FREQUENCY IN GOATS
Table 1. Morphological parameters of udder, milk partitioning, milk composition, and SCC of 3 dairy goat breeds milked once (×1) or twice
(×2) daily1,2
Goat breed
Majorera
Parameter3
Initial UD (cm)
Final UD (cm)
ΔCF (cm)
ΔTF (cm)
Cisternal milk (%)
Fat (%)
Protein (%)
Lactose (%)
TS (%)
SNF (%)
Alveolar milk (%)
Fat (%)
Protein (%)
Lactose (%)
TS (%)
SNF (%)
SCC (log/mL)
Tinerfeña
P-value4
Palmera
×1
×2
×1
×2
×1
×2
SEM
B
F
B×F
29.10a
29.95a
0.85
0.25
81.63a
3.70
3.57bc
4.92
12.85a
9.19a
18.37b
6.03b
3.52
4.78ab
15.03b
9.00
6.00b
28.10ab
28.80ab
0.70
0.05
80.21ab
3.66
3.55bc
4.90
12.80ab
9.14a
19.79ab
4.84d
3.54
4.87a
13.94c
9.12
5.90b
26.65abc
28.60ab
1.95
1.35
81.62ab
3.63
3.59abc
4.78
12.73ab
9.07ab
18.38ab
5.86bc
3.59
4.74ab
14.73bc
9.00
6.33a
25.55bc
27.10ab
1.55
1.10
82.04a
3.47
3.44c
4.78
12.39b
8.92b
17.96b
4.94cd
3.50
4.76ab
13.89c
8.96
6.26ab
24.80c
26.30b
1.50
0.35
77.78b
3.78
3.80a
4.79
13.10a
9.29a
22.22a
7.07a
3.69
4.58c
16.05a
8.98
6.08b
25.00c
25.60b
0.60
0.15
78.23b
3.83
3.68ab
4.87
13.08a
9.25a
21.77a
6.45ab
3.58
4.70b
15.38ab
8.99
5.92b
0.422
0.507
0.293
0.227
0.524
0.049
0.040
0.023
0.073
0.038
0.524
0.166
0.039
0.022
0.163
0.036
0.051
0.001
0.021
0.40
0.11
0.007
0.11
0.049
0.083
0.012
0.011
0.007
0.001
0.51
0.001
0.001
0.61
0.010
0.41
0.26
0.42
0.64
0.86
0.60
0.21
0.70
0.32
0.26
0.86
0.001
0.47
0.046
0.002
0.71
0.25
0.74
0.94
0.87
0.999
0.68
0.66
0.76
0.64
0.58
0.79
0.68
0.66
0.79
0.52
0.82
0.68
0.93
a–d
Means with different superscripts within the same row are different (P < 0.05).
Data are least squares means and standard error of means.
2
Morphological parameters were recorded before the first and the last milking of the experimental period. Milk parameters were measured at
24- and 14-h milking intervals for ×1 and ×2 goats, respectively.
3
UD = udder depth; ΔCF = difference between initial and final cistern-floor (CF) distance; ΔTF = difference between initial and final teat-floor
(TF) distance.
4
B = breed; F = milking frequency.
1
with observations in dairy cows by Waldmann et al.
(1999) and dairy ewes by McKusick et al. (2002).
Milk protein percentage was unaffected by milk partitioning (Table 1). This agrees with observations in
dairy ewes by McKusick et al. (2002) and dairy cows
by Ayadi et al. (2004), indicating that casein micelles
passed more freely than fat globules from the alveolar
to the cisternal compartment between milkings, resulting in minimal differences in protein concentration of
milk fractions.
Lactose content in cisternal milk was not affected
by milking frequency (Table 1). Lactose content in
alveolar milk in Majorera and Tinerfeña breeds was
not different between ×1 and ×2 goats, whereas in the
Palmera breed, lactose content was lower for ×1 goats
(P < 0.05). The decrease in milk lactose percentage
seems to be due to lactose passing from milk into blood
through an impaired tight junction (Stelwagen et al.,
1994) associated with extended milking intervals.
The results for the SCC showed that Tinerfeña goats
presented higher values than Majorera and Palmera
goats for ×1. Nevertheless, no differences in SCC level
were found for ×2 between the studied breeds (Table
1). Harmon (1994) indicated that variability in SCC
within a breed is greater than variability in SCC be-
tween breeds; therefore, it is possible that the results
found could be due to an effect of individual variability.
Milking frequency did not affect the milk SCC. No
coincident data exist about the effect of milking frequency on SCC levels. Salama et al. (2003) did not
find significant differences in SCC between ×1 and ×2
goats in 32 Murciano-Granadina goats during an entire
lactation, whereas Komara et al. (2009) conducted 2
experiments with Alpine goats and found differences
only in experiment 1, which could be due to the different number of goats used in each experiment (48 for
experiment 1 and 8 for experiment 2) and to individual
variability, as indicated by the authors.
No udder halves presented clinical mastitis during
the experimental period, suggesting that ×1 does not
impair udder health and indicating that the breeds are
fully adapted to this milking frequency. Lacy-Hulbert
et al. (2005) did not report differences in the number
of clinical or subclinical infections between ×1 and ×2
in dairy cows. Nudda et al. (2002) suggested that high
SCC levels induced by a change in milking frequency
may be temporary and not necessarily due to mammary gland infections.
In conclusion, the fact that about 80% of total milk
was stored in cisternal compartments for 14- and 24-h
Journal of Dairy Science Vol. 96 No. 2, 2013
73
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
1074
TORRES ET AL.
milking intervals suggested a greater transfer of milk
from the alveoli to the cistern during early udder filling and, therefore, did not produce significant changes
in the milk composition. However, milking intervals
caused diverse changes in the milk composition in the
alveolar fraction, especially in fat, lactose, and TS
contents; therefore, it merits further investigation of
the mechanisms responsible for milk ejection between
milkings.
Komara, M., M. Boutinaud, H. Ben Chedly, J. Guinard-Flament, and
P. G. Marnet. 2009. Once-daily milking effects in high-yielding
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Lacy-Hulbert, S. J., D. E. Dalley, and D. A. Clark. 2005. The effects
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N.Z. Soc. Anim. Prod. 65:137–142.
López, J. L., J. Capote, G. Caja, S. Peris, N. Darmanin, A. Argüello,
and X. Such. 1999. Changes in udder morphology as a consequence
of different milking frequencies during first and second lactation in
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Wageningen Pers, Wageningen, the Netherlands.
McKusick, B. C., D. L. Thomas, Y. M. Berger, and P. G. Marnet.
2002. Effect of milking interval on alveolar versus cisternal milk
accumulation and milk production and composition in dairy ewes.
J. Dairy Sci. 85:2197–2206.
Nudda, A., R. Bencini, S. Mijatovic, and G. Pulina. 2002. The yield
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Peaker, M. 1980. The effect of raised intramammary pressure on mammary function in the goat in relation to the cessation of lactation.
J. Physiol. 301:415–428.
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Knight. 2004. Changes in cisternal udder compartment induced by
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M. P. Marín, and A. Martí. 2003. Effects of once versus twice daily
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ACKNOWLEDGMENTS
This work was supported by Fondo Europeo de Desarrollo Regional-Instituto Nacional de Investigación
y Tecnología Agraria y Alimentaria (FEDER-INIA)
RTA2009-00125.
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Journal of Dairy Science Vol. 96 No. 2, 2013
74
ARTÍCULO 2
ARTÍCULO 2
G Model
RUMIN-4519;
No. of Pages 6
ARTICLE IN PRESS
Small Ruminant Research xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Small Ruminant Research
journal homepage: www.elsevier.com/locate/smallrumres
Comparison between two milk distribution structures in
dairy goats milked at different milking frequencies
A. Torres a , N. Castro b , A. Argüello b , J. Capote a,∗
a
b
Instituto Canario de Investigaciones Agrarias (ICIA), La Laguna 38200, Tenerife, Spain
Department of Animal Science, Universidad de Las Palmas de Gran Canaria, Arucas 35413, Spain
a r t i c l e
i n f o
Article history:
Received 6 March 2013
Received in revised form 26 April 2013
Accepted 30 April 2013
Available online xxx
Keywords:
Milk yield
Milk partitioning
Milking frequency
Dairy goat
a b s t r a c t
Twenty-four dairy goats of 3 breeds (Majorera, Tinerfeña, and Palmera) in mid lactation
(110 ± 7 d in milk) were milked unilaterally at 2 frequencies (once: X1 or twice daily: X2)
for 6 wk to evaluate milk yield and milk composition and to compare two milk distribution structures. On the sampling days, milk volumes of each udder halves were recorded
and analyzed. Milk partitioning was divided into: cisternal (CM) and alveolar milk (AM);
and into: machine milk (MM), machine stripping milk (MSM), and residual milk (RM). In
Majorera and Tinerfeña breeds did not find significant differences in milk yield and milk
composition due to milking frequency. In contrast, Palmera goats had an increase of 14%
in milk yield when they were milked X2 compared with X1, but the protein content was
significantly higher in the milk of X1 (3.92%) than X2 (3.72%). Furthermore, the absence
of differences in protein daily yield between X1 and X2, suggested that cheese yield could
not be maintained. Milking frequency did not affect CM and AM percentages in the studied
breeds. Regarding breed factor, Majorera and Palmera had the highest and lowest CM percentages, respectively, both in X1 and X2. On the other hand, MM and MSM percentages did
not differ due to milking frequency in Tinerfeña and Palmera breeds. However, Majorera
goats had significant differences in MM (77.29 vs. 71.66%) and MSM (12.67 vs. 17.41%) for
X1 and X2, respectively. A breed effect was observed on MM and MSM fractions: Majorera goats had higher MM percentages, while Tinerfeña and Palmera goats had higher MSM
percentages. RM fraction was not affected by milking frequency or breed factors. Finally, no
significant correlation coefficients were detected when comparing CM and AM with MM,
MSM and RM fractions, which indicates that both milk partitioning structures did not seem
to be comparable between them, at least in goat udders that have a more horizontal teat
insertion.
© 2013 Elsevier B.V. All rights reserved.
1. Introduction
a separate teat (Bruckmaier and Blum, 1998). According
to Wilde and Knight (1990), the unilateral alteration of
milking frequency indicates that milk yield changes are
imposed by local intramammary mechanisms and affects
only the treated gland. In addition, Wall and McFadden
(2008) explained that experimental design that applied
single gland milking eliminated variation among animals
due to environment, nutrition and genetic factors and
exposed each gland to the same systemic factors.
Milk is stored in two interconnected anatomical udder
compartments that determine the milkability (Salama
The mammary glands in ruminants are composed of
functionally separate glands (four in cows and two in
goats and sheep). Each gland has its own secretory tissue and cisternal cavities, and each gland is drained by
∗ Corresponding author at: ICIA, Apto. de correos 60, La Laguna 38200,
Tenerife, Spain. Tel.: +34 922542800; fax: +34 922542898.
E-mail addresses: [email protected], [email protected] (J. Capote).
0921-4488/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
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et al., 2004). Cisternal milk (CM) is located in the cisternal
compartment consisting of the gland cistern, the teat cisterns and the large ducts; while alveolar milk (AM) is stored
within the alveoli and small interlobular ducts (Marnet and
McKusick, 2001). Milk partitioning between both compartments varies according to specie, breed, age, lactation stage,
parity and milking interval (Salama et al., 2004; Castillo
et al., 2008). Partitioning between CM and AM was formerly determined by drainage of cisternal milk, by using a
teat cannula (Peaker and Blatchford, 1988), but new techniques include the use of an oxytocin receptor antagonist
to block spontaneous milk ejection (Wellnitz et al., 1999).
Differing from dairy cows, small ruminants have proportionally larger cisterns which play an important role
in the storage of milk between milkings and can greatly
affect the removal of milk at the time of milking (Marnet
and McKusick, 2001). Furthermore, udder morphology of
many goat and sheep breeds is characterized by having a
more horizontal teat insertion (Rovai et al., 2008; Torres
et al., 2013), a circumstance that implies manual intervention for complete milk removal. Milk collected during
milking can be divided into: machine milk (MM) obtained
between attaching the line and the final cessation of the
milk flow without the operator having to manipulate the
udder; and machine stripping milk (MSM) which requires
manual intervention to remove milk not obtained by the
machine. Moreover, a milk fraction known as residual milk
(RM) remains in the mammary tissue and it can only be collected after administration of pharmacological amounts of
oxytocin (Bruckmaier and Blum, 1998).
The goals of this study were to evaluate the effects of
unilateral milking frequency on milk yield, milk composition and milk component yield; and to compare two milk
distribution structures in 3 dairy goat breeds milked at 2
frequencies, and whether there are relevant correlations
among them to establish a relationship between CM and
AM with MM, MSM and RM.
daily for X2, according to Capote et al. (2008). Fat (4.0%)-corrected milk
(FCM) was calculated according to Salama et al. (2003). Milk samples were
analyzed immediately after collection to determine milk composition. Fat,
protein, lactose and total solids were determined using a MilkoScan 133
analyzer (Foss Electric, Hillerod, Denmark). Milk composition of X2 was
calculated by a weighted average from the a.m. and the p.m. milk composition. Milk component yields were calculated by multiplying milk yield
by corresponding milk component percentages.
Milk partitioning was calculated at the a.m. milking (24- and 14-h
milking intervals for X1 and X2, respectively). During wk 1, 3, and 5, on
the sampling days, each goat was injected intravenously with 0.8 mg of
an oxytocin receptor blocking agent (Tractocile; Ferring, Madrid, Spain)
inside a holding pen immediately before entering the milking parlor to
record CM volume. After CM removal, the goats were injected intravenously with 2 IU of oxytocin (Oxiton; Laboratorios Ovejero, León, Spain)
to reestablish milk ejection, and AM was measured. During wk 2, 4, and 6,
on the sampling days, milk partitioning was divided into MM, MSM performed by the same milker, and RM obtained after injecting goats with
2 IU of oxytocin.
A MIXED model procedure (SAS 9.0; SAS Institute Inc., Cary, NC) was
used. The statistical model included the fixed effects of milking frequency
(X1 or X2) and breed (Majorera, Tinerfeña, or Palmera), the random effect
of the half-udder nested within animal, the respective interactions, and
the residual error:
Yijk = � + Bi + Mj + Gk + (BM)ij + εijk
where Yijk is the observation of the dependent variable, � is the overall
mean, Bi is the effect of the breed i (i = 3), Mj is the effect of the milking frequency j (j = 2), Gk is the random effect, (BM)ij is the effect of the interaction
between breed and milking frequency, εijk is the residual error.
Differences among the breeds and milking frequencies were evaluated
using a multiple comparison test following the Tukey–Kramer method.
Pearson’s correlation coefficients between milk fractions were also calculated. Statistical differences were considered significant at P < 0.05. Data
are presented as least squares means.
3. Results
Milk yield and FCM (Table 1) did not differ due to milking frequency in Majorera and Tinerfeña breeds (P > 0.05).
Nevertheless, Palmera breed had a significant increase in
milk yield by 14% when they were milked X2 compared
with X1. Furthermore, FCM of X2 was higher than in X1
udder halves by 18% in Palmera goats (P < 0.05). Regarding
breed effect, Majorera goats had higher milk yield values
than Palmera goats both in X1 and X2 (P < 0.05).
No differences were found in fat percentages in the studied breeds (Table 1) when the milking frequency effect was
considered (P > 0.05). Besides, Palmera breed had higher
milk fat content than Majorera and Tinerfeña both in X1 and
X2, but the differences were significant only in X2. Milking
frequency did not have effect on the protein percentages in
Majorera and Tinerfeña goats (Table 1). However, Palmera
goats had higher milk protein content in X1 than in X2
udder halves (P < 0.05). Regarding breed effect, Majorera
and Tinerfeña had lower protein fraction than Palmera both
in X1 and X2 (P < 0.05).
No significant differences were detected in lactose content among breeds and milking frequencies (Table 1),
ranging from 4.78 to 4.86% in the studied conditions. Likewise, total solids percentages were not affected due to
milking frequency (Table 1) (P > 0.05). Moreover, differences in total solids percentages were found when the
breed effect was considered (P < 0.05). Thus, Palmera goats
had higher values than Majorera and Tinerfeña both in X1
and X2.
2. Materials and methods
The experimental animal procedures were approved by the Ethical
Committee of the Universidad de Las Palmas de Gran Canaria (Arucas,
Spain). A total of 24 dairy goats in mid lactation (110 ± 7 DIM) of Majorera
(n = 8; 2.7 ± 0.4 L/d; parity = 3.4 ± 1.1), Tinerfeña (n = 8; 2.3 ± 0.5 L/d; parity = 3.1 ± 1.3), and Palmera (n = 8; 1.8 ± 0.4 L/d; parity = 3.1 ± 1.2) breeds
from the experimental farm of the Instituto Canario de Investigaciones
Agrarias (ICIA, Tenerife, Spain) were used. The animals were fed with commercial concentrate, maize, lucerne, wheat straw and a vitamin–mineral
corrector in accordance with the guidelines issued for lactating goats
by Institut National de la Recherche Agronomique (INRA, Paris, France;
Jarrige, 1990). The milking frequency before the start of the experimental
period was once per day. Goats were milked in a double 12-stall parallel milking parlor equipped with recording jars (4 L ±5%) and a low-line
milk pipeline. Milking was performed at a vacuum pressure of 42 kPa, a
pulsation rate of 90 pulses/min, and a pulsation ratio of 60/40. The milking routine included wiping dirt off teat ends and stripping 2–3 squirts
of milk from each teat, machine milking, machine stripping before cluster removal, and teat dipping in an iodine solution (P3-cide plus; Henkel
Hygiene, Barcelona, Spain).
During a 6-wk period, goats were milked once daily in the left mammary gland (X1; at 07:00 h), whereas the right mammary gland was
milked twice daily (X2; at 07:00 and 17:00 h). Before the start of the experimental period, the goats were exposed to 3 wk of adaptation to X2. Milk
volumes were measured by using the recording jars in the milking parlor
for each udder half. On the sampling days (wk 2, 4, and 6), milk yield was
recorded as MM plus MSM once daily for X1, and MM and MSM twice
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Table 1
Milk yield, milk composition and milk component yield of each udder half of three dairy goat breeds milked once (X1) or twice (X2) daily.a
Parameter
Goat breed
SEM
Majorera
Tinerfeña
X1
X2
1.39ab
1.34a
3.79b
3.67bc
4.83
Milk yield (L/d)
FCMb (L/d)
Fat (%)
Protein (%)
Lactose (%)
X2
1.27ab
1.21ab
3.76b
3.63bc
4.85
13.06b
a
a
59.42
54.40a
73.65a
46.90
44.78ab
61.70ab
180.42a
197.58a
162.07ab
Fat (g/d)
Protein (g/d)
Lactose (g/d)
52.47
50.95a
67.20ab
Total solids (g/d)
X1
1.51a
1.50a
3.94b
3.59c
4.86
12.99b
Total solids (%)
Palmera
X1
1.31ab
1.28a
3.88b
3.51c
4.83
12.92b
12.91b
ab
X2
1.04c
1.05b
4.06ab
3.92a
4.78
ab
50.00
44.73ab
64.22ab
1.19b
1.24a
4.29a
3.72b
4.81
0.049
0.045
0.060
0.041
0.028
13.58a
13.53a
0.083
b
a
1.785
1.504
2.513
161.42a
5.936
41.77
40.79b
49.96c
168.04a
141.01b
50.98
44.45ab
57.48b
a–c
Means with different superscripts within the same row are different (P < 0.05).
a
Data are least squares means and standard error of means.
b
FCM = total milk yield (L/d) × (0.400 + 0.150 × total fat content (%)).
r = −0.93; Palmera, r = −0.86). In addition, no significant
correlation coefficients were found between MSM and RM
for X1 and X2. Finally, CM and AM were not correlated with
MM, MSM and RM fractions in the studied breeds milked
at X1 and X2 (P > 0.05).
Majorera and Tinerfeña goats were not different in milk
component yields between X1 and X2 (Table 1). In contrast,
Palmera goats had significant increases by 22%, 15%, and
14% in X2 daily yields of fat, lactose and total solids, respectively, compared with X1. However, protein yield did not
significantly increase as did the other milk components.
CM and AM percentages (Table 2) did not differ due to
milking frequency in the studied breeds (P > 0.05). Majorera
and Palmera had the highest and lowest CM percentages,
respectively, both in X1 and X2 (P < 0.05). In the same way,
MM and MSM percentages (Table 2) were not affected
by milking frequency in Tinerfeña and Palmera breeds
(P > 0.05). However, Majorera goats had higher and lower
values in MM and MSM fractions, respectively, in X1 with
regard to X2. RM percentages were not affected by the milking frequency and breed factors (P > 0.05), ranging from
10.66 to 14.49% in the studied conditions.
Correlation coefficients among milk fractions are
reported in Table 3. High negative correlations between
MM and MSM fractions (P < 0.05) were observed for
X1 (Majorera, r = −0.76; Tinerfeña, r = −0.94; Palmera,
r = −0.90) and X2 (Majorera, r = −0.72; Tinerfeña, r = −0.70;
Palmera, r = −0.90). Moreover, MM and RM were only significantly correlated for X1 (Majorera, r = −0.82; Tinerfeña,
4. Discussion
The increase in milk yield in Palmera goats was higher
than the values reported in Tinerfeña goats (6%) by Capote
et al. (1999) and Damascus goats (7%) by Papachristoforou
et al. (1982) and similar to loss caused by X1 in Alpine
goats (16%) by Komara et al. (2009). The increase in FCM
in Palmera goats was comparable with the FCM value
reported in Murciano-Granadina goats (18%) by Salama
et al. (2003). However, the goats of those studies were
milked with the same frequency in both glands. The unilateral milking frequency effect indicates that the increase in
milk yield is a response strictly at the level of the mammary gland via local factors, and not due to the greater
availability of nutrient supply caused by the suppression
of milking in the opposite gland (Nudda et al., 2002; Wall
and McFadden, 2008).
Table 2
Milk fractions of three dairy goat breeds milked once (X1) or twice (X2) daily.a,b
Fractionc
Goat breed
SEM
Majorera
CM (%)
AM (%)
MM (%)
MSM (%)
RM (%)
Tinerfeña
Palmera
X1
X2
X1
X2
X1
X2
82.28a
18.41c
77.29a
12.67c
10.66
81.75a
18.77c
71.66b
17.41b
11.61
80.12ab
20.15bc
67.21bc
19.71b
12.96
80.30ab
19.99bc
61.21c
24.94ab
14.49
77.22bc
23.02ab
65.86bc
22.34ab
12.48
76.70c
23.43a
59.07c
27.57a
13.24
0.528
0.498
1.366
1.100
0.449
a–c
Means with different superscripts within the same row are different (P < 0.05).
Data are least square means and standard error of means.
Milk fractions were measured at 24- and 14-h milking intervals for X1 and X2 goats, respectively.
c
CM, cisternal milk; AM, alveolar milk; MM, machine milk; MSM, machine stripping milk; RM, residual milk.
a
b
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Table 3
Pearson’s correlation coefficients matrix among milk fractions of three dairy goat breeds milked once (above diagonal) or twice (below diagonal) daily.
Breed
Fractiona
CM
AM
MM
MSM
RM
−0.885*
−0.989*
−0.987*
−0.285
0.084
−0.051
0.379
−0.050
0.162
0.181
−0.159
0.007
−0.007
−0.189
0.008
−0.245
0.143
−0.136
0.173
0.232
0.023
−0.761*
−0.941*
−0.897*
−0.823*
−0.933*
−0.863*
CM
Majorera
Tinerfeña
Palmera
AM
Majorera
Tinerfeña
Palmera
−0.892*
−0.935*
−0.990*
MM
Majorera
Tinerfeña
Palmera
0.411
0.067
0.617
−0.550
−0.082
−0.586
MSM
Majorera
Tinerfeña
Palmera
−0.164
0.158
−0.615
0.314
−0.210
0.636
−0.721*
−0.702*
−0.895*
RM
Majorera
Tinerfeña
Palmera
0.128
−0.476
0.024
0.053
0.433
−0.107
−0.050
−0.253
−0.406
*
a
0.139
0.694
0.666
−0.258
−0.107
0.006
P < 0.05.
CM, cisternal milk; AM, alveolar milk; MM, machine milk; MSM, machine stripping milk; RM, residual milk.
X1 regimen due to selection for high cistern capacity. The
physiological explanation relates to the suggestion that casein f(1–28) is effective only in the alveoli where it is
in contact with the epithelial cells. Exposing the alveoli to
high concentration of -casein f(1–28) will induce disruption of the tight junction (Silanikove et al., 2010).
Milk fat content was not affected by milking frequency
which is in accordance with Komara et al. (2009), who also
did not observe differences in fat globule size between X1
and X2 for Alpine goats. However, Salama et al. (2003)
showed that milk of X1 goats had a 10% more fat content than milk of X2 goats. Milk fat is considered to be
the most variable component in ruminant milk, due to
differing regulatory mechanisms for secretion of milk fat
globules relative to the components in the aqueous phase
of milk and to the transfer between alveolar and cisternal compartments (Salama et al., 2003). X1 management
in high-yielding goats is a potent stressor that is able to
disturb alveolar milk ejection because alveolar milk was
shown to contain up to 75% of milk fat when milk ejection
was inhibited (Labussière, 1988). However, the absence of
significant differences in the studied breeds might be due
to the fact that approximately 80% of total milk was stored
in the cisternal compartment and most of the transfer of
milk fat from the alveoli to the cistern had already taken
place.
Milk protein concentration was significantly higher in
X1 than in X2 udder halves in Palmera goats, which agrees
with observations in dairy goats by Komara et al. (2009)
and dairy ewes by Nudda et al. (2002). Salama et al. (2003)
explained that the concentration effect of the protein in X1
with respect to X2 was due to the milk volume, this was
lower with X1 but the casein synthesized remained and
became more concentrated in the milk.
In goats, Capote et al. (1999) found that milking frequency did not affect lactose percentage and reiterate the
assertion that lactose is the milk component least influenced by breed and milking factors, indicating a similar
The differences observed in milk yield in Majorera, Tinerfeña and Palmera goats between X1 and X2 may be
explained as a consequence of cisternal capacity of each
breed (Bruckmaier and Blum, 1998). A large voluminous
cistern takes more time in filling up, delaying the effects
of the intramammary feedback inhibitor, intramammary
pressure, or tight junction integrity on milk transference
from the alveoli to the cisterns, during the filling of the
udder (Capote et al., 2008). Recently, serotonin has been
proposed as a feedback inhibitor of lactation, being a component involved in milk regulation (Hernandez et al., 2008).
However, milk yields did not differ between treatment and
control halves, which suggest that serotonin is not a local
factor.
In addition, Silanikove et al. (2000) showed in goats
and cows that the plasmin-induced -casein f(1–28) peptide can serve as a local regulator on milk secretion by
functioning as a potassium channel blocker, which was
subsequently confirmed in dairy cows by Silanikove et al.
(2009). It is predicted that for milking intervals of less than
20 h in goats and 18 h in cows, the concentration of caseinderived peptides, including the active component -casein
f(1–28), would be higher in the cistern than in the alveoli;
therefore, the alveoli will not be exposed to the full impact
of the negative feedback signal of this peptide. Extending
milk stasis beyond these times exceeds the storage capacity of the cistern, resulting in the equilibration of -casein
f(1–28) concentration between the cistern and the alveoli
(Silanikove et al., 2010).
Thus, animals with smaller udder size, and hence of
cisternal compartment, such as Palmera goats (SuárezTrujillo et al., 2013; Torres et al., 2013), are more affected
by mechanisms of feedback inhibition. Silanikove et al.
(2010) explained that high milk producing goats, as Saanen, selected to high alveolar to cistern compartment ratio,
are the most sensitive to changes in milking frequency. In
contrast, medium milk producing goats, as some Spanish
breeds, may attain their genetic potential for milk yield in
Please cite this article in press as: Torres, A., et al., Comparison
tion structures in dairy goats milked at different milking frequencies.
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reported in Murciano-Granadina (9–11%; Peris et al., 1996)
and Tinerfeña (7–12%; Capote et al., 2009) goats.
In addition, Marnet and McKusick (2001) reported significant increases in MSM percentage without proportional
modification of AM or CM volume in Lacaune ewes between
the years 1982 and 1992. The increase in MSM fraction was
a consequence of the tendency to have more horizontally
placed teats in the udder which increases cisternal storage capacity to improve milk production (Bruckmaier et al.,
1997; Marnet and McKusick, 2001).
High negative correlations observed between MM and
MSM fractions both in X1 and X2 in the studied breeds differs with these observed by Peris et al. (1996) and Caja et al.
(1999) who did not find significant correlations between
both fractions. However, it is clear that the correlation
between both them could help in the selection of goats to
improve the milkability. Furthermore, Peris et al. (1996)
noted that the negative correlation between MM and RM
in goats could reduce the milking time because they accumulate more milk into the cisterns.
Although, CM and AM (Salama et al., 2004) or MM, MSM
and RM percentages (Capote et al., 2008) have a strong
dependence on udder morphology, the absence of significant correlation coefficients between CM and AM with
MM, MSM, and RM fractions impeded the establishment of
a relationship between both milk partitioning structures,
at least in goat udders that have a more horizontal teat
insertion.
performance of the synthetic activity of the mammary
gland.
In the studied breeds there were no significant
differences found in total solids content between X1
and X2. There is disagreement about the milking frequency effects on total solids percentages. Capote et al.
(1999) had observed a lower total solids fraction in
X1 (12.48%) than X2 (12.84%), while for Salama et al.
(2003) the total solids were higher in X1 (13.60%) than
X2 (12.90%) in goats during an entire lactation. Finally,
the fact that Palmera goats had higher percentages of
total solids than Majorera and Tinerfeña both in X1
and X2, may be explained because the Palmera had
higher percentages of fat and protein than the other two
breeds.
The increases in fat, lactose, and total solids yields were
consistent with the significant increase in the milk production of Palmera goats. However, the absence of differences
in protein yield between X1 and X2 can be explained by
a lower concentration of protein in X2, suggesting that
cheese yield could not be maintained. Marnet and Komara
(2008) explained that the regulation of milk components
synthesis is dependent on the duration of the milking
interval, which can influence cheese-making capacity and
cheese quality.
Despite the differences in milk yield in Palmera goats
between X1 and X2, there were not differences in the distribution of milk in the udder. Salama et al. (2004) did not
find differences in milk accumulation rates in the cisternal
compartment at 16 and 24 h in Murciano-Granadina goats
milked X1 or X2, whereas Torres et al. (2013) suggested that
the high percentages of milk stored in cisternal compartments for 14- and 24-h milking intervals may be explained
by a greater transfer of milk from the alveoli to the cisterns
during early udder filling. The differences in milk partitioning among breeds were due to the cisternal size of each
breed that influences the capacity to store milk in this compartment. For example, Rovai et al. (2008) found CM–AM
ratio of 59–41 and 77–23 for Manchega and Lacaune
ewes, respectively, where Lacaune breed presented a
greater cisternal area than Manchega breed (24.0 vs.
12.4 cm2 ).
MM and MSM percentages were higher and lower,
respectively, in X1 udder halves in the studied breeds, but
the differences were significant only in Majorera goats.
Previously, Capote et al. (2009) found no differences in
MM percentages between X1 (67.8%) and X2 (64.5%) in
Tinerfeña goats of high milk production, while MSM percentages were higher in X2 (27.8%) than X1 (20.7%), and
RM percentages were higher in X1 (11.5%) than X2 (7.7%),
suggesting that an increase in milking frequency in a normal routine implies greater stimulation and thus a higher
milk drop to the cisterns. Moreover, Majorera goats had
a higher and lower MM and MSM percentages, respectively, than Tinerfeña and Palmera goats. Caja et al. (1999)
explained that quantities of milk in each partition obtained
by mechanical milking depend on the udder morphology
and the development of cisternal and canalicular systems;
which suggests a high variability between breeds and even
between animals of same breed. RM percentages were not
affected by the breed, and they were similar than those
5. Conclusion
The results demonstrated that X2 practice did not
improve the milk production of the Majorera and Tinerfeña breeds, so it is a consequence of the adaptation
of these breeds to X1, which is an interesting issue in
goat production systems, because it requires fewer variable
costs. Nevertheless, the high increase in milk yield in the
Palmera goats due to X2 could seem a profitable management at certain times during the lactation. However, this
practice did not produce an increased in milk protein yield
in accordance with milk yield. Therefore, other studies are
required to evaluate how the milking frequency affects the
cheese yield, which is a very important part of the Canary
Islands livestock economy. Additionally, the knowledge of
the structures of milk partitioning can serve as a basis for
future selection programs to improve the milkability of the
studied breeds. Furthermore, if a wider selection of breeds
could be studied, ranging from low milk yielding to high
milk yielding breeds, the relationship among milk fractions
would be more noticeable.
Conflict of interest
None.
Acknowledgment
This work was supported by Fondo Europeo de
Desarrollo Regional-Instituto Nacional de Investigación y
Tecnología Agraria y Alimentaria (FEDER-INIA) RTA200900125.
Please cite this article in press as: Torres, A., et al., Comparison
tion structures in dairy goats milked at different milking frequencies.
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between two milk distribuSmall Ruminant Res. (2013),
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Salama, A.A.K., Caja, G., Such, X., Peris, S., Sorensen, A., Knight, C.H., 2004.
Changes in cisternal udder compartment induced by milking interval
in dairy goats milked once or twice daily. J. Dairy Sci. 87, 1181–1187.
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blocks K+ channels on the apical membranes. Life Sci. 67, 2201–2212.
Silanikove, N., Shapiro, F., Shinder, D., 2009. Acute heat stress brings down
milk secretion in dairy cows by up-regulating the activity of the milkborne negative feedback regulatory system. BMC Physiol. 9, 13.
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exploiting goat’s milk: quality, safety and production aspects. Small
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Suárez-Trujillo, A., Capote, J., Argüello, A., Castro, N., Morales-delaNuez, A.,
Torres, A., Morales, J., Rivero, M., 2013. Effects of breed and milking
frequency on udder histological structures in dairy goats. J. Appl. Anim.
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Torres, A., Castro, N., Hernández-Castellano, L.E., Argüello, A., Capote, J.,
2013. Effects of milking frequency on udder morphology, milk partitioning, and milk quality in 3 dairy goat breeds. J. Dairy Sci. 96,
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ruminants. J. Dairy Sci. 81, 939–949.
Caja, G., Capote, J., López, J.L., Peris, S., Such, X., Argüello, A., 1999. Milk partitioning and milk flow rate of Canarian dairy goats under once daily
or twice daily milking frequencies. In: Barillet, F., Zervas, N.P. (Eds.),
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The effects of milking once or twice daily throughout lactation on milk
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Please cite this article in press as: Torres, A., et al., Comparison
tion structures in dairy goats milked at different milking frequencies.
http://dx.doi.org/10.1016/j.smallrumres.2013.04.013
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between two milk distribuSmall Ruminant Res. (2013),
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Short-term effects of milking frequency on milk yield, milk composition, SCC and
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milk protein profile in dairy goats
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Alexandr Torres1, Lorenzo-Enrique Hernández-Castellano2, Antonio
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Morales-delaNuez2, Davinia Sánchez-Macías3, Isabel Moreno-Indias2,
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Noemi Castro2, Juan Capote1 and Anastasio Argüello2*
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1
Instituto Canario de Investigaciones Agrarias, La Laguna, Tenerife 38200, Spain.
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2
Department of Animal Science, Universidad de Las Palmas de Gran Canaria, Arucas
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35413, Spain.
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Agroindustrial Engineering Department, Universidad Nacional de Chimborazo.
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Riobamba 060150, Ecuador.
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* Corresponding author: Anastasio Argüello, Fac. Veterinaria s/n, 35413 Arucas, Spain.
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Tel.: +34 928451094; fax: +34 928451142. E-mail address: [email protected]
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
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The goats in Canary Islands are milked once daily by tradition, but in other areas, is
26
carried out two times, with an increase of milk yield. Therefore it is important know if
27
the increase of milking frequency can improve the production without impairing the
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milk quality. The objective of this study was to investigate the short term effects of 3
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milking frequencies on milk yield, milk composition, SCC, and milk protein profile in
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dairy goats traditionally milked once a day. Twelve Majorera goats in early lactation (48
31
± 4 d in milk) were used to determine the milk yield, milk composition, somatic cell
32
count, and milk protein profile at 3 different milking frequencies. During a 5-wk period,
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goats were milked once a day (X1) at wk 1 and 5, twice a day (X2) at wk 2 and 4, and
34
three times a day (X3) at wk 3. Milk recording and sampling were done on the last day
35
of each experimental week. Milk yield increased by 26% from X1 to X2. No differences
36
were obtained when switched from X2 to X3, and from X3 to X2. The goats recovered
37
the production level when they returned to X1. Different patterns of changes in the milk
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constituents due to milking frequency were observed. Fat percentages increased when
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switched from X1 to X2, there was a significant decrease from X2 to X3, and continued
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to decline as milking frequency was decreased. Protein and lactose percentages were
41
similar among X1, X2, and X3. SCC values were similar when goats were milked X1,
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X2, and X3, but then increased slightly when milking frequency returned to X2 and X1.
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Finally, different patterns were observed for caseins (αS1-CN, αS2-CN, β-CN, κ-CN).
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Thus, milking frequency did not affect the proportion of αS1-CN in milk, while αS2-CN
45
and β-CN increased from X1 to X2, stayed stable from X2 to X3, and then decreased as
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milking frequency decreased. In contrast, κ-CN decreased from X1 to X2, and
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recovered to initial values when milking frequency was returned to X1.
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Keywords: milking frequency, milk yield, milk quality, dairy goat.
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Goat research needs progress rapidly to reach the level of knowledge of other
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species like cattle or sheep, especially in milk production (Argüello, 2011). Many
52
studies seek to implement management systems in dairy farms with extended milking
53
intervals, or to minimize additional cost associated with extra milking if it is
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outweighed by the value of additional milk obtained as observed in dairy cows (Wall &
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McFadden, 2008). Milking is done twice daily (X2) in countries with high-yielding
56
dairy goats (Capote et al. 2009). However, dairy farmers want to reduce their labor
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requirements associated with milking, to devote time to other farm practices or to social
58
activities (Komara et al. 2009). In this way, the practice of once daily milking (X1) is
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viewed with interest by dairy farmers. In contrast, thrice daily milking (X3) is a
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relatively novel management practice and it is not generally used in small ruminants,
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but in dairy cows it has emerged as an effective management tool for dairy farmers to
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increase milk production (Wall & McFadden, 2008).
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Silanikove et al. (2010) explained that high milk producing goats, as Saanen,
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selected to high alveolar to cistern compartment ratio, are the most sensitive to changes
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in milking frequency. In contrast, medium milk producing goats, as Majorera, may
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attain their genetic potential for milk yield in X1 regimen due to selection for high
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cistern capacity (Torres et al. 2013). Previous studies revealed losses in milk yield of
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X1 of 8 to 45% compared to X2 (Mocquot & Auran, 1974; Capote et al. 2009) and
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increases of 8 to 28% when the goats were milked X3 instead of X2 (Henderson et al.
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1985; Boutinaud et al. 2003). The wide variation in milk yield due to milking frequency
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in the literature reports is a consequence of differences in breed, lactation stage, level of
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production, duration of X1, X2 or X3, and individual characteristics (Marnet &
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Komara, 2008). Additionally, the regulation of milk components synthesis and somatic
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
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cells are dependent on the milking intervals, which can influence on the milk quality
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(Marnet & Komara, 2008).
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The hypothesis of this research paper is that 3 milking frequencies might have
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minor effect on milk yield and chemical composition in a goat breed that is generally
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milked X1. In addition, no information regarding the influence of milking interval on
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milk protein profile in dairy goats is available. Therefore, the objective of this study was
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to investigate the short term effects of 3 milking frequencies on milk yield, milk
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composition, SCC, and milk protein profile in dairy goats traditionally milked X1.
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Materials and Methods
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The experimental animal procedures were approved by the Ethical Committee of
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the Universidad de Las Palmas de Gran Canaria. A total of 12 Majorera goats were in
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second parity with 48 ± 4 DIM at the beginning of the experiment. The goats which
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were used in the experiment were from the experimental farm of the Faculty of
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Veterinary of this University. Kids were separated from their dams within 8 h of birth.
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The milking frequency before the start of the experimental period was once per day.
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During a 5-wk period, goats were milked: once daily at wk 1 and 5 (X1, at 09:00), twice
91
daily at wk 2 and 4 (X2, at 09:00 and 17:00), and thrice daily at wk 3 (X3, at 09:00,
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13:00, and 19:00). The animals had access to wheat straw ad libitum and a vitamin-
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mineral corrector. The supplement per goat was 800 g/d of alfalfa and 1200 g/d of a mix
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of maize, lucerne, and dehydrated beetroot, which it meets the nutritional requirements
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in accordance with the guidelines issued for lactating goats by Institut National de la
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Recherche Agronomique (INRA, Paris, France; Jarrige, 1990). The amount of
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supplement did not differ according to milking frequency. Goats were milked in a
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double 12-stall parallel milking parlor (Alfa Laval Iberia SA, Madrid, Spain) equipped
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with recording jars (4 L ± 5%) and a low-line milk pipeline. Milking was performed at a
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vacuum pressure of 42 kPa, a pulsation rate of 90 pulses/min, and a pulsation ratio of
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60/40, in accordance with Capote et al. (2009). The milking routine included machine
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milking and stripping milking, done by the operator to remove the remaining milk from
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the udder before cluster removal; and teat dipping in an iodine solution (P3-cide plus;
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Henkel Hygiene, Barcelona, Spain).
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Milk recording and sampling were done on the last day of each experimental
106
week. Milk yield (L/d) was calculated by adding milk volume at every milking by using
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the recording jars in the milking parlor. Milk samples (50 ml) were analyzed
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immediately after collection at the a.m. milking to determine milk composition, SCC,
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and milk protein profile. Fat, protein, lactose, and total solids percentages were
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determined using a DMA2001 Milk Analyzer (Miris Inc., Uppsala, Sweden), and SCC
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using a DeLaval somatic cell counter (DeLaval International AB, Tumba, Sweeden).
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Milk proteins were separated by SDS-PAGE (12.5%) using a Bio-Rad slab
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electrophoresis unit (Bio-Rad Laboratories, Hercules, CA, USA), based on the method
114
of Laemmli (1970). Protein concentration of the milk was determined with the Quick
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Start™ Bradford Protein Assay (Bio-Rad Laboratories, Hercules, CA, USA), using
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BSA as standard reference. Gels were loaded with a fixed protein level (40 µg) per line,
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and were run at 200 V for 6 h. After electrophoresis, gels were stained for 90 min using
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10% acetic acid, 40% methanol, and 0.05% (w/v) Coomassie Blue R-250 solution, and
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then were destained for 15 h using 10% acetic acid and 40% methanol solution. The gel
120
images (Figure 1) were scanned (Gel Doc EQ, Bio-Rad Laboratories), and the relative
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quantities of each band were determined by using the Quantity One software program
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(Bio-Rad Laboratories). Each sample was analyzed on duplicate gels. Individual protein
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y parámetros de calidad de la leche en las cabras canarias
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species were identified by comparing their relative mobilities with those of standard
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proteins (Precision Plus ProteinTM Unstained Standards, Bio-Rad Laboratories).
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The statistical analyses were performed by using SPSS 15.0 software (SPSS
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Inc., Chicago, IL). Repeated measures analysis of variance (ANOVA), with adjustments
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for non-sphericity (Greenhouse-Geisser correction), was applied to evaluate time-
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dependent milking frequency effects on milk yield and milk quality; followed by LSD
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post-hoc tests. Statistical differences were considered significant at P < 0.05. Data are
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presented as least squares means.
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Results and Discussion
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Milk yield increased by 26 ± 10% (P < 0.05) with increasing milking frequency
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from X1 to X2 (Table 1). This increase in Majorera goats, which are traditionally
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milked X1, was similar to loss caused by X1 (compared with X2) in Saanen goats
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(26%) in late lactation reported by Boutinaud et al. (2003) during a short treatment
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period (23 d). Subsequently, no significant differences in milk yield were obtained
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between X2 and X3. This result does not agree with those of Boutinaud et al. (2003)
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who found significant increases (8%) in milk yield for goats milked X3 compared with
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X2. Finally, when the milking frequency was returned to X1, there was a recovery in
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milk yield to initial values (P > 0.05). Previously, Capote et al. (2009) showed that
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Tinerfeña goat breed, also generally milked X1, did not present significant increases
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from X1 to X2 (9%) in high production level (> 2.4 L/d); but medium (between 1.9 and
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2.4 L/d) and low (< 1.9 L/d) production level presented significant increases (25 and
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20%, respectively) for 24 wks of lactation, suggesting that lower difference between X1
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and X2 in high production goats is a consequence of a wider cisternal capacity which
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allows a continuous drop of alveolar milk to the cistern, reducing the feedback inhibitor
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process and the intramammary pressure. Otherwise, the absence of increase from X2 to
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X3 indicated that secretory activity of mammary cells was not modified at these
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frequencies in goats usually milked X1.
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Fat percentage had a significant increase when switched from X1 to X2, there
152
was a significant decrease from X2 to X3, and continued to decline as milking
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frequency was decreased (Table 1). The higher fat content of X2 milk compared to X1
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may be due to the length of the preceding milking interval, in X2 was 16 h and in X1
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was 24 h. However, McKusick et al. (2002) in dairy ewes and Torres et al. (2013) in
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dairy goats explained that transfer of milk fat from the alveoli to the cistern occurs
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during early udder filling, and this transfer no longer takes place during later intervals.
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In addition, some researchers have observed no effect of milking frequency on fat
159
percentage (Komara et al. 2009), whereas other studies have found a negative
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correlation between milk yield and fat percentages due to milking frequency (Salama et
161
al. 2003). Capote et al. (1999) found that goats milked X2 showed a significant increase
162
in fat percentage compared to those animals milked X1, due to a higher proportion of
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alveolar milk removed by X2 which is richer in fat. However, a decline in milk fat
164
fraction was observed when milking frequency was changed to X3 and then returned to
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X2. Some research works on dairy ruminants studied the association of plasma cortisol
166
levels with different factors that cause stress as related to milking (Hopster et al. 2002;
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Negrao et al. 2004). Previously, Raskin et al. (1973) found that cortisol may produce a
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decrease in milk lipid formation from glucose and acetate. Therefore, more experiments
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will be necessary to study the relationship between frequent milking and cortisol levels
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in goats usually milked X1.
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Milking frequency did not affect the protein percentages during the experimental
172
period (P > 0.05; Table 1). In accordance, Torres et al. (2013) reported no differences in
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y parámetros de calidad de la leche en las cabras canarias
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milk protein percentages due to milking frequency in cisternal and alveolar fractions of
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3 dairy breeds traditionally milked X1. However, Boutinaud et al. (2003) showed a
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higher protein content in Saanen goats milked X1 compared with X2 and X3, which
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suggested a specific leakage of serum protein into milk after modification of the
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permeability of the mammary epithelium at longer milking intervals. Nevertheless, the
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ability to support the extended intervals between milking of some dairy goat breeds
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could be related to the capacity of the tight junctions to remain tight for a long period,
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without modification of secretion of milk components regulated by it (Marnet &
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Komara, 2008).
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Similarly to protein percentages, lactose concentration was unaffected by the
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studied milking intervals (P > 0.05; Table 1). This is in agreement with the results by
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Henderson et al. (1985) between X2 and X3 in Saanen goats and with Torres et al.
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(2013) between X1 and X2 in Majorera goats. In this way, Capote et al. (1999)
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reiterated the assertion that lactose is the lactic component least influenced by breeding
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and milking factors, indicating a similar performance of the synthetic activity of the
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mammary gland.
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Total solids stayed stable from X1 to X2 (P > 0.05; Table 1), and decreased from
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X2 to X3 (P < 0.05). No corresponding results for X3 are available in dairy goats for
191
comparison, but Capote et al. (1999) and Salama et al. (2003) reported significant
192
differences in total solids percentages (12.48 vs.12.84% and 13.60 vs.12.90% for X1
193
and X2, respectively) in dairy goats during an entire lactation. The milk total solids are
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a mixture of fat, protein, lactose and mineral matter. Thus, any variation on these
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constituents can affect its concentration. In this case, milk fat was the most variable
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component among milking frequencies, which involved changes in total solids
197
percentages.
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SCC values were unaffected by milking frequency when goats were milked X1,
199
X2, and X3; but then increased slightly when milking frequency returned to X2 and X1
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(Table 1). There is disagreement about the milking frequency effects on SCC levels.
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Some researchers have observed no effect of frequent milking on SCC in cows (Klei et
202
al. 1997), and ewes (de Bie et al. 2000), both in early lactation. Boutinaud et al. (2003)
203
showed that SCC tended to increase in X1, whereas it remained stable in X3 compared
204
with X2 in dairy goats. Likewise, Lakic et al. (2011) explained that prolonged milking
205
intervals as well as short milking intervals have influence on the milk SCC in cows.
206
Kamote et al. (1994) suggested that the increase in SCC in extended milking intervals in
207
dairy cows could be explained by a concentration effect. Paape et al. (2001) described
208
those stressful events as changes in the milking routine, to which goats are very
209
sensitive, may cause an increase in SCC even in the absence of an intramammary
210
infection. Therefore, the high values of SCC obtained during the final period seem to be
211
related with a physiological stress to the mammary gland caused by the experiment.
212
Changes in milk protein profile were found due to milking frequency (Table 2).
213
Thus, different patterns were observed for caseins (αS1-CN, αS2-CN, β-CN, κ-CN).
214
Milking frequency did not affect the proportion of αS1-CN in milk, while αS2-CN and β-
215
CN increased from X1 to X2 (P < 0.05), stayed stable from X2 to X3, and then
216
decreased as milking frequency decreased. In contrast, κ-CN decreased from X1 to X2
217
(P < 0.05), and recovered to initial values when milking frequency was progressively to
218
X3 toward X1 (P > 0.05). Goats showed a significantly lower β-Lactoglobulin (β-Lg)
219
content in the final week of experimentation, whereas α-Lactalbumin (α-La) presented a
220
lower percentage when animals were milked X3. Lastly, there was not an effect of
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milking frequency on lactoferrin (LF) and serum albumin (SA) concentration when
222
increasing from X1 to X3 (P > 0.05), and then had an enhanced trend when the milking
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y parámetros de calidad de la leche en las cabras canarias
223
frequency returned to X1. Immunoglobulin G heavy- (IgH) and light-chain (IgL) had a
224
decrease in concentrations from X1 to X2, but these differences were significant only
225
for IgL, then were maintained from X2 to X3, and tended to increase at the end of the
226
experiment.
227
The results for caseins are consistent with observations in dairy cows by
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Sorensen et al. (2001), who found higher proportions of α-CN and β-CN and lower κ-
229
CN when switched from X2 to X3 in either the long or the short term. However, these
230
authors indicated that β-Lg and α-La were not affected by milking frequency in the
231
short term. Regarding to SA, it has the same amino acid sequence as the blood serum
232
molecule, and it is commonly believed that SA enters the milk by leaking through the
233
epithelial tight junction from the systemic fluids, as was suggested by Boutinaud et al.
234
(2003). However, Shamay et al. (2005) showed that SA is produced and secreted by
235
epithelial cells into milk, indicating that it is part of the mammary gland innate immune
236
system. In addition, Hernández-Castellano et al. (2011) found that high milking
237
frequency affected the immunological milk parameters in Majorera goats, chiefly a
238
decreased on IgG concentration (immunosupression) presumably due to an increased in
239
the cortisol excretion by adrenal glands, caused by animal stress.
240
The changes in milk protein profile in cows have been associated with differing
241
proteolytic enzyme activities, such as plasmin, because the increase of milking
242
frequency reduces the time that milk is stored in the udder, and the time to degrade the
243
milk proteins is shorter (Sorensen et al. 2001). Previously, Bastian (1996) indicated that
244
plasmin causes degradation of β-CN to γ-CN, which influence the milk quality for
245
cheese production, and Grieve & Kitchen (1985) explained that κ-CN is more resistant
246
to proteolysis for bovine plasmin than α-CN and β-CN, which can explain that κ-CN
247
varied at the opposite to β-CN and αS2-CN when milking frequency was increased from
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X1 to X2. However, Svennersten-Sjaunja et al. (2007) reported a lower plasmin activity
249
when milking frequency was increased in dairy cows, but proteolytic degradation of
250
milk proteins was maintained. Therefore, more experiments will be necessary to
251
evaluate the plasmin activity at different milking frequencies and its effects on
252
degradation of milk proteins in dairy goats.
253
In conclusion, short-term changes of the normal milking frequency in goats
254
traditionally milked X1 during early lactation can affect milk production as reflected the
255
high increase in milk yield when milking frequency was increased from X1 to X2.
256
However, the changes in milk quality, especially in the fat content and milk protein
257
profile, requires new studies on how the milking frequency affect the yield and quality
258
of the cheeses, because the goat milk in Canary Islands is used mainly for cheese
259
production. In addition, the modification in milk yield did not take place when goats
260
were switched from X2 to X3, but the decreased in fat content requires further studies to
261
evaluate the factors that cause this decline.
262
263
This research was supported by grant AGL 2006-08444/GAN from the Spanish
264
Government. The authors want to thank A. Alavoine, G. Pons, V. Bissières, and S.
265
Cyrille from École Vetérinaire de Toulouse (France) for their technical assistance
266
during the experiment.
267
268
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Paape MJ, Poutrel B, Contreras A, Marco JC & Capuco AV 2001 Milk somatic cells
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bovine mammary gland. Journal or Dairy Science 88 569–576
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Sorensen A, Muir DD & Knight CH 2001 Thrice-daily milking throughout lactation
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of Dairy Research 68 15–25
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Svennersten-Sjaunja K, Wiking L, Edvardsson A, Bavius A-K, Larsen LB & Nielsen
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JH 2007 Effect of frequent milking on milk fat and protein. Journal of Animal
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Torres A, Castro N, Hernández-Castellano LE, Argüello A & Capote J 2013 Effects of
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milking frequency on udder morphology, milk partitioning, and milk quality in 3
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dairy goat breeds. Journal of Dairy Science 96 1071–1074
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Wall EH & McFadden TB 2008 Use it or lose it: Enhancing milk production efficiency
by frequent milking of dairy cows. Journal of Animal Science 86 27–36
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359
360
361
362
363
364
365
366
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368
369
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y parámetros de calidad de la leche en las cabras canarias
370
Table 1. Milk yield, milk composition, and SCC from dairy goats milked at different
371
milking frequencies†‡
Milking Frequency§
X1
X2
X3
X2
X1
SEM
P value
Milk yield (L/d)
1.69b
2.13a
2.09a
2.01a
1.89b
0.127
0.001
Fat (%)
3.86b
4.38a
3.61b
3.34c
3.13c
0.084
0.001
Protein (%)
3.39
3.06
3.07
3.03
3.12
0.054
0.073
Lactose (%)
5.17
5.09
5.26
5.21
5.22
0.035
0.514
Total Solids (%)
13.24a
13.34a
12.74b
12.26c
12.30c
0.109
0.001
SCC (log/ml)
5.99ab
5.82b
5.88ab
6.21a
6.06a
0.077
0.050
372
a–c
373
† Data are least squares means and standard error of means
374
‡ Milk composition and SCC were determined with milk samples from a.m. milking for
375
X2 and X3
376
§ X1 = once daily; X2 = twice daily; X3 = thrice daily
Means with different superscripts within the same row are different (P < 0.05)
377
378
379
380
381
382
383
384
385
386
16
100
MANUSCRITO 3
387
Table 2. Protein profile from dairy goats milked at different milking frequencies†‡
Milking Frequency§
Protein (%)¶
X1
X2
X3
X2
X1
SEM
P value
αS1-CN
11.15
10.41
11.67
10.03
10.36
0.399
0.302
αS2-CN
16.22bc
20.86a
20.63a
18.05b
15.70c
0.975
0.001
β-CN
21.63b
25.95a
25.29a
24.39ab
22.85b
0.692
0.021
κ-CN
12.01a
9.24b
9.64b
8.29b
9.84ab
0.513
0.038
β-Lg
14.67a
15.44a
14.68a
15.39a
12.96b
0.449
0.045
α-La
10.43a
10.30ab
8.73b
9.95ab
11.52a
0.509
0.050
LF
3.02b
1.57b
2.10b
3.66ab
4.97a
0.558
0.007
SA
3.91ab
2.40b
3.22b
4.89a
5.30a
0.501
0.001
IgH
3.74ab
2.38b
2.61ab
3.28ab
4.20a
0.390
0.042
IgL
3.17a
1.45b
1.43b
2.09ab
2.31ab
0.421
0.010
388
a–c
389
†Data are least squares means and standard error of means
390
‡Protein profile was determined with milk samples from a.m. milking for X2 and X3
391
§ X1 = once daily; X2 = twice daily; X3 = thrice daily
392
¶ CN = casein; β-Lg = β-lactoglobulin; α-La = α-lactalbumin; LF = lactoferrin; SA =
393
serum albumin; IgH = immunoglobulin G heavy-chain; IgL = immunoglobulin G light-
394
chain
Means with different superscripts within the same row are different (P < 0.05)
395
396
397
398
399
17
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
400
Figure 1. SDS-PAGE patterns of milk proteins from dairy goats (lanes 1–9 and 11–13)
401
milked at different milking frequencies (X1 = once daily; X2 = twice daily; X3 = thrice
402
daily).
403
18
102
MANUSCRITO 4
MANUSCRITO 4
1
Effects of oxytocin treatments on milk production in dairy goats
2
A. Torres,* J. Capote,* A. Argüello,† D. Sánchez-Macías,‡ A. Morales-delaNuez,†
3
and N. Castro,†1
4
*Instituto Canario de Investigaciones Agrarias, La Laguna, Tenerife 38200, Spain.
5
†Department of Animal Science, Universidad de Las Palmas de Gran Canaria, Arucas
6
35413, Spain.
7
‡Universidad Nacional de Chimborazo, Riobamba 060150, Ecuador.
8
1
9
Tel.: +34 928451093; fax: +34 928451142. E-mail address: [email protected]
Corresponding author: Noemi Castro, Fac. Veterinaria s/n, Arucas 35413, Spain.
10
11
ABSTRACT
12
Two experiments were conducted to determine the effects of oxytocin treatments on
13
milk ejection. In experiment 1, 39 dairy goats in mid lactation (95 ± 10 days in milk)
14
were divided into 3 groups (n = 13) with similar milk yields. During an 8-wk period,
15
goats from group 1 (OT1) were introduced to the milking parlor once a week, 10 h after
16
morning milking, and all pre-milking routines were carried out, including stripping 2 to
17
3 squirts of milk from each teat, but the animals were not milked. During this period,
18
goats from group 2 (OT2) were injected intravenously with 2 IU of oxytocin in the
19
crowd pen once a week, 10 h after morning milking, but the animals were not milked.
20
Goats from group 3 (control) remained in the pen without any treatment. In experiment
21
2, 10 dairy goats in mid lactation (104 ± 5 days in milk) were divided into 5 groups (n =
22
2) with similar milk yields. During a 6-wk period, goats were milked once daily, except
23
for one day a week, when they were milked 3 additional times (at 1200, 1600, and 2000
24
h). On this day, after each milking, goats were administered intravenously with a dose
25
corresponding to oxytocin (0.5, 1, 2, and 4 IU), or saline solution (control). Machine
1
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
26
milk and residual milk were recorded for each group. Additionally, milk yield, chemical
27
composition, and SCC of each group were determined for the 3 following days after
28
applying the treatments. In experiment 1, milk yield and milk composition were not
29
affected by OT1 and OT2, indicating that the oxytocin release by the stimulatory effect
30
of milking procedures or the administration of synthetically manufactured oxytocin,
31
have no galactopoietic effect on goats not milked immediately. In experiment 2, milk
32
partitioning and milk composition did not differ due to oxytocin treatments at 1200,
33
1600 and 2000 h, indicating that the contraction of the myoepithelial cells that surround
34
the mammary alveoli is similar between low and high doses of oxytocin. In addition, the
35
evolution of milk yield and SCC after the experimental day was not affected by the
36
treatments with oxytocin.
37
38
Keywords: oxytocin, dairy goat, milk yield, milk partitioning.
39
INTRODUCTION
40
41
In ruminants, milk ejection is a neuroendocrine reflex arc and it occurs in
42
response to suckling, manual stimulation of the mammary gland, or machine milking
43
(Macuhova et al., 2004). These stimulations cause on the udder the release of oxytocin
44
from the neural lobe of the pituitary into blood circulation, which induces contraction of
45
myoepithelial cells that surround the alveoli where milk is stored, and transfer it into the
46
cisternal space (Lollivier et al., 2002; Bruckmaier, 2003). However, not all alveolar
47
milk can be ejected if milk is not removed from the udder (Bruckmaier and Blum,
48
1998).
49
Depending on the stimulation of the mammary gland, it causes different
50
oxytocin responses. Suckling is a more potent stimulus than milking, while hand
2
106
MANUSCRITO 4
51
milking induces a more pronounced release of oxytocin than machine milking (Akers
52
and Lefcourt, 1982; Gorewit et al., 1992). Furthermore, prestimulation before milking is
53
important because it increases oxytocin levels and promotes early induction of milk
54
ejection to avoid an interruption of milk flow during early milking (Bruckmaier, 2001).
55
However, milk ejection during machine milking is not complete, even with an adequate
56
prestimulation. Usually a residual milk fraction remains in the udder which can be
57
obtained by injection of oxytocin, and it varies widely between breeds and even
58
between animals of the same breed (Peaker and Blatchford, 1988; Such et al., 1999).
59
Milk ejection in goats, in response to oxytocin, is similar to cows and sheep, but
60
milk removal is different due to udder morphology and milk partitioning (Bruckmaier
61
and Blum, 1998). In goats, oxytocin release is highly variable within and between
62
animals, being readily induced by tactile prestimulation or by the milking machine
63
(Bruckmaier and Blum, 1998; Marnet and McKusick, 2001).
64
In experiments of unilateral milking frequency of dairy goats, the effect of
65
oxytocin on milk yield and milk composition of the unmilked gland is still unknown.
66
For this reason, the first objective of the present study was to determine the effects of
67
endogenous and exogenous oxytocin on milk parameters in goats not milked
68
immediately. In addition, the second objective was to study the response to different
69
doses of exogenous oxytocin on milk ejection in dairy goats.
70
71
72
MATERIALS AND METHODS
Animal and Management Conditions
73
Two experiments were conducted on a total of 49 dairy goats in mid lactation.
74
The experiment 1 was performed on the experimental farm of the Instituto Canario de
75
Investigaciones Agrarias (Tenerife, Spain) on 39 dairy goats, while the experiment 2
3
107
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
76
was carried out on the experimental farm of the Faculty of Veterinary of the
77
Universidad de Las Palmas de Gran Canaria (Arucas, Spain) on 10 dairy goats. The
78
experimental animal procedures were approved by the Ethical Committee of the
79
Universidad de Las Palmas de Gran Canaria. The animals were fed with maize, lucerne,
80
dehydrated beetroot, wheat straw, and a vitamin-mineral corrector in accordance with
81
the guidelines issued for lactating goats by Institut National de la Recherche
82
Agronomique (INRA, Paris, France; Jarrige, 1990). In both experiments, goats were
83
milked in a double 12-stall parallel milking parlor equipped with recording jars (4 L ±
84
5%) and a low-line milk pipeline. Milking was performed at a vacuum pressure of 42
85
kPa, a pulsation rate of 90 pulses/min, and a pulsation ratio of 60/40, in accordance with
86
Capote et al. (2006). The milking routine included wiping dirt off teat ends and
87
stripping 2 to 3 squirts of milk from each teat; machine milking and stripping milking,
88
done by the operator to remove the milk remaining in the udder before cluster removal;
89
and teat dipping in an iodine solution (P3-cide plus; Henkel Hygiene, Barcelona, Spain).
90
91
Experimental Procedures
92
Experiment 1. 39 Canarian dairy goats in second parity, with 95 ± 10 DIM,
93
were divided into 3 groups (n = 13) with similar milk yields. All goats were milked
94
once daily (at 0700 h) according to the normal milking routine. During an 8-wk period,
95
goats from group 1 (OT1) were introduced to the milking parlor once a week, 10 h after
96
morning milking, and all pre- and post-milking routines were carried out, including
97
stripping 2 to 3 squirts of milk from each teat and dipping of teats in an iodine solution
98
(P3-cide plus; Henkel Hygiene, Barcelona, Spain), but the animals were not milked.
99
Before the experimental period, OT1 goats were exposed to 3 wk of adaptation, where
100
the animals began to enter the milking parlor in the afternoon. During the experimental
4
108
MANUSCRITO 4
101
period, goats from group 2 (OT2) were injected intravenously with 2 IU of oxytocin
102
(Oxiton; Laboratorios Ovejero, León, Spain) in the crowd pen once a week, 10 h after
103
morning milking, but the animals were not milked at this time. Goats from group 3
104
(control) remained in the pen without any treatment. Milk recording and sampling were
105
done the next day at the morning milking.
106
Experiment 2. 10 Canarian dairy goats in second parity, with 104 ± 5 DIM,
107
were divided into 5 groups (n = 2) with similar milk yields. During a 6-wk period, goats
108
were milked once daily (at 0800 h), except one day a week, when they were milked 3
109
additional times (at 1200, 1600, and 2000 h). On this day, milk was collected after each
110
milking (machine milk), and after the complete cessation of milk flow, the groups were
111
injected intravenously with a dose corresponding to oxytocin (0.5, 1, 2, and 4 IU), or
112
saline solution (control) to remove the remainder of milk in the udder (residual milk).
113
Total milk was defined as machine milk plus residual milk. Additionally, milk yield,
114
milk composition (fat, protein and lactose), and SCC of each group were determined for
115
the 3 following days after applying the treatments.
116
In experiment 1, milk volumes were recorded by using the recording jars in the
117
milking parlor, while milk of each fraction of the experiment 2 was measured by a
118
graduated cylinder. Milk samples (experiment 1 and 2) were analyzed immediately after
119
collection to determine chemical composition. Fat, protein and lactose percentages were
120
determined by using a DMA2001 Milk Analyzer (Miris Inc., Uppsala, Sweden), and
121
SCC using a DeLaval somatic cell counter (DeLaval International AB, Tumba,
122
Sweeden).
123
124
Statistical Analysis
125
The statistical analyses were performed by using SPSS 15.0 software (SPSS
126
Inc., Chicago, IL). Repeated measures analysis of variance (ANOVA), with adjustments
5
109
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
127
for non-sphericity (Greenhouse-Geisser correction), was applied to evaluate time-
128
dependent effects of OT1 and OT2 on milk yield and milk composition (experiment 1),
129
and doses of oxytocin on milk partitioning and milk composition (experiment 2),
130
followed by LSD post-hoc tests. Differences among experimental groups (experiment 1
131
and 2) were evaluated using a multiple comparison test following the Tukey method.
132
Statistical differences were considered significant at P < 0.05. Data are presented as
133
estimated marginal means.
134
RESULTS AND DISCUSSION
135
136
Experiment 1.
137
In the 3 studied groups, it was observed, as expected, a decrease in milk yield at
138
the end of the experimental period (P < 0.05; Table 1). Capote et al. (2008) observed a
139
significant decrease in milk yield throughout lactation in dairy goats (2.51 vs. 2.08 L/d
140
in 12 and 20 weeks of lactation, respectively). The decline in milk production with
141
advancing lactation has been attributed to a gradual decrease in number of secretory
142
cells (Knight and Peaker, 1984). No differences were detected in milk yield (P > 0.05)
143
in any week of experimentation due to treatments. Therefore, the results indicate that
144
the oxytocin release by the stimulatory effect of milking procedures or the
145
administration of synthetically manufactured oxytocin, have no galactopoietic effect in
146
goats not milked immediately. Some studies have indicated that oxytocin release is not
147
an important factor for milk yield gain in small ruminants with large cisterns (Negrao et
148
al., 2001; Marnet and McKusick, 2001). However, it has been indicated that oxytocin
149
doses induce an increase in milk yield proportional to the capacity of cisternal storage
150
but only when accompanied by milk removal (Lollivier and Marnet, 2005a).
6
110
MANUSCRITO 4
151
Oxytocin treatments did not affect the milk composition (Table 1). Lollivier and
152
Marnet (2005b) observed changes in protein content due to oxytocin injection in dairy
153
goats not milked immediately (28.9 vs. 27.6 g/kg in control and oxytocin group,
154
respectively), but fat (33.2 vs. 34.3 g/kg) and lactose contents (44.9 vs. 45.3 g/kg) were
155
unaffected. In cows, Caja et al. (2004) demonstrated a back-flux of milk to the ductal
156
and alveolar compartments when they are not milked promptly after milk letdown,
157
which influences the transference of milk components, as the upward movement of the
158
fat globules in the opposite direction to the downward draining and newly secreted milk
159
(Ayadi et al., 2004). However, Salama et al. (2004) indicated the absence of recoil and
160
milk return from cistern to alveoli in goats, due to the greater cisternal milk percentages
161
and the small contact surface between the alveolar and cisternal compartments.
162
163
Experiment 2.
164
Total milk volumes and percentages of machine milk and residual milk at 1200,
165
1600 and 2000 h are presented in Table 2. No differences were observed in total milk
166
volumes due to treatments at different milking times (P > 0.05). Since the control goats
167
were not subjected to a complete emptying of the udder, the milk accumulated in the
168
alveoli and small ducts was transferred to the cistern and was obtained in the next
169
milking; while the other goats began to store milk in the alveolar tissue which was
170
ejected after having received doses of oxytocin. Thus, there was no effect of treatments
171
on total milk volume within the udder. On the other hand, percentages of residual milk
172
obtained after saline solution injection were lower (P < 0.05) in control group (< 20%)
173
than oxytocin groups (ranged from 38.31 to 59.79%) at 1200, 1600 and 2000 h, which
174
corroborate that oxytocin has an effect on the milk transfer from alveolar tissue to
175
cistern. Moreover, the absence of differences in the milk partitioning among the 4
7
111
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
176
oxytocin groups at these intervals (P > 0.05), could indicate that the contraction of the
177
myoepithelial cells that surround the mammary alveoli is similar between low and high
178
doses of oxytocin. Previously, Lollivier et al. (2002) have indicated that a complete
179
milk removal is obtained following intravenous injection with 0.1 to 1 IU of oxytocin in
180
dairy goats.
181
Fat, protein and lactose percentages in machine and residual milk are shown in
182
Table 3. Fat percentages in machine milk significantly decreased between 1200 and
183
1600 h for the studied groups, and although another decline was observed between 1600
184
and 2000 h, the differences were not significant. A similar pattern was detected in fat
185
fractions of residual milk for the oxytocin groups between 1200 and 1600h. This decline
186
in milk fat content of both fractions could be due to cortisol released in response to the
187
stress caused by the experiment. Some research work on dairy ruminants studied the
188
association of plasma cortisol levels with different factors that cause stress in animals
189
(e.g., milking) (Hopster et al., 2002; Negrao et al., 2004). Previously, Raskin et al.
190
(1973) found that cortisol may produce a decrease in milk lipid formation from glucose
191
and acetate. In addition, no differences were observed in fat percent in milk fractions
192
among oxytocin groups at any studied milking time (P > 0.05). Gorewit and Sagi (1984)
193
observed that fat percentage in total residual milk was not affected by administration of
194
different doses of oxytocin (0.5, 1, 1.5, 2, and 3 IU) in dairy cows, but they used
195
different experimental techniques for determination of residual milk.
196
Protein and lactose percentages in machine milk and residual milk were not
197
affected due to oxytocin doses at 1200, 1600 and 2000 h (P > 0.05). In cows, some
198
authors claim that there is no modification of milk protein and lactose contents
199
regardless if oxytocin is administered over medium or long periods of time, indicating
200
that the effect of oxytocin is not manifested through an effect on cell activity (Nostrand
8
112
MANUSCRITO 4
201
et al., 1991; Ballou et al., 1993). However, Gorewit and Sagi (1984) observed that milk
202
protein percentage was lower for those cows receiving higher doses of oxytocin,
203
attributed to a dilution effect as a result of increased total milk yield.
204
Milk yield, chemical composition and SCC before (day 0) and after (day 1–3)
205
injecting different treatments are presented in Table 4. In all groups, an expected
206
decrease in milk yield at day 1 after applying the treatments was observed (P < 0.05).
207
This was because 12 hours had elapsed since the last milking. Therefore, the goats
208
stored less milk inside the udder. However, there was no effect due to treatments on
209
milk production in the following days (P > 0.05), recovering similar values to day 0.
210
Bruckmaier (2003) and Macuhova et al. (2004) found a reduction of milk ejection when
211
chronic oxytocin treatment (50 IU) was withdrawn in dairy cows. It seems that the
212
reduction of spontaneously removed milk was caused by reduced contractibility of
213
myoepithelial cells in the mammary gland at the normal physiological oxytocin
214
concentrations (Macuhova et al., 2004).
215
Fat percentages declined significantly at days 1 and 2 in all studied groups, but
216
at day 3 it reached similar values to day 0 (Table 4). In contrast, protein contents
217
increased at days 1 and 2, and subsequently decreased. Lactose percentages did not
218
show significant changes in the following days after experiment. This behavior could be
219
due to different regulatory mechanisms for secretion of milk components. No statistical
220
differences were found in SCC levels for the experimental days in the oxytocin groups
221
(Table 4). Allen (1990) observed that milk SCC increased in a dose dependent manner
222
at 12, 24, 36, 48, 60, and 72 h after the injected dose (1, 10, 100, or 1000 IU), and some
223
cows had a mastitis-like response with clots in the milk. Finally, variability of SCC
224
among the groups was high, and may be due to multiple individual factors (e.g., oestrus)
225
and not necessarily a response caused by treatments.
9
113
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
226
CONCLUSIONS
227
228
The oxytocin release by the stimulatory effect of milking procedures or the
229
administration of synthetically manufactured oxytocin had no galactopoietic effect and
230
did not produce apparent changes in the milk composition on goats not milked
231
immediately, and that are traditionally milked once a day. Likewise, it did not produce
232
apparent changes in the milk composition. In addition, the absence of differences in the
233
milk partitioning and milk composition among the administration of 4 doses of oxytocin
234
indicated that the contraction of the myoepithelial cells that surround the mammary
235
alveoli is similar between low and high doses of oxytocin in dairy goats milked once a
236
day by tradition.
237
ACKNOWLEDGMENTS
238
239
This work was supported by Fondo Europeo de Desarrollo Regional-Instituto
240
Nacional de Investigación y Tecnología Agraria y Alimentaria (FEDER-INIA)
241
RTA2009-00125.
242
243
REFERENCES
244
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oxytocin and prolactin in parturient dairy cows. Horm. Behav. 15:87–93.
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Allen, J. C. 1990. Milk synthesis and secretion rates in cows with milk composition
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changed by oxytocin. J. Dairy Res. 73:975–984.
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Ayadi, M., G. Caja, X. Such, M. Rovai, and E. Albanell. 2004. Effect of different
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milking intervals on the composition of cisternal and alveolar milk in dairy
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251
Ballou, L. U., J. L. Bleck, G. T. Bleck, and R. D. Bremel. 1993. The effects of daily
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Caja, G., M. Ayadi, and C. H. Knight. 2004. Changes in cisternal compartment based on
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Capote, J., A. Argüello, N. Castro, J. L. López, and G. Caja. 2006. Correlations between
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Lollivier, V., and P. G. Marnet. 2005a. Galactopoietic effect of milking in lactating
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Holstein cows: Role of physiological doses of oxytocin. Livest. Prod. Sci.
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Lollivier, V., and P. G. Marnet. 2005b. Comparative study of the galactopoietics effect
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Nostrand S. D., D. M. Galton, H. N. Erb, and D. E. Bauman. 1991. Effects of daily
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Peaker, M., and D. R. Blatchford. 1988. Distribution of milk in the in the goat
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mammary gland and its relation to the rate and control of milk secretion. J. Dairy
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Raskin, R. L., M. Raskin, and R. L. Baldwin. 1973. Effects of chronic insulin and
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Salama, A. A. K., G. Caja, X. Such, S. Peris, A. Sorensen, and C. H. Knight. 2004.
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Changes in cisternal udder compartment induced by milking interval in dairy
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goats milked once or twice daily. J. Dairy Sci. 87:1181–1187.
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Such, X., G. Caja, and L. Pérez. 1999. Comparison of milking ability between
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Manchega and Lacaune dairy ewes. Pages 45–50 in Milking and milk
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production of dairy sheep and goats. EAAP Publication No. 95. F. Barillet and
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N. P. Zervas, Wageningen Pers., Wageningen, The Netherlands.
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319
320
321
322
323
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
324
Table 1. Milk yield and milk composition of goats subjected to different oxytocin treatments.1
Experimental weeks
Parameter
Treatment
Fat (%)
Protein
(%)
Lactose
(%)
1
2
3
2.13
a
2.15
a
2.15
a
2.10
a
OT2
2.04
a
1.98
a
Control
4.62
4.63
OT1
4.34
OT2
4
2.05
a
2.14
a
5
6
2.04
a
2.08
a
2.06
a
4.56
4.67
4.72
4.55
4.48
4.34
4.42
4.44
4.52
Control
3.82
3.80
OT1
3.81
OT2
Control
Milk
yield
(L/d)
2
2.05
a
2.09
a
2.06
a
7
2.05
a
1.95
2.03
1.84
0.060
0.072
1.92
1.83
b
0.055
4.78
4.72
4.86
0.040
4.37
4.40
4.40
4.55
0.048
4.60
4.48
4.68
4.75
4.76
0.037
3.81
3.83
3.86
3.87
3.88
3.89
0.016
3.79
3.75
3.79
3.77
3.79
3.80
3.81
0.014
3.88
3.83
3.84
3.88
3.86
3.89
3.92
3.93
0.013
Control
5.02
5.04
5.06
4.97
5.02
4.93
4.92
4.88
0.021
OT1
5.11
5.13
5.09
5.07
5.12
5.06
4.99
4.94
0.015
OT2
5.05
5.05
5.09
5.01
5.09
5.01
5.01
4.92
0.023
1.95
ab
ab
b
ab
2.05
1.98
SEM
b
b
OT1
ab
8
ab
325
a–b
326
1
Data are estimated marginal means and standard error of means.
327
2
Treatment: OT1 = endogenous oxytocin; OT2 = exogenous oxytocin.
1.85
Means with different superscripts within the same row are different (P < 0.05).
328
329
330
331
332
333
334
335
336
337
338
339
14
118
MANUSCRITO 4
340
Table 2. Total milk volume and milk partitioning of goats injected with different doses of
341
oxytocin at 4-h milking intervals.1
Milking time (h)
Parameter
Treatment
1200
1600
2000
SEM
Control
277.42
244.58
248.92
21.517
0.5 IU
264.17
278.17
329.83
13.037
1 IU
278.58
225.42
265.00
9.762
2 IU
285.00
263.83
290.42
14.550
4 IU
290.67
277.67
297.33
14.616
Control
82.48x
81.92x
87.94x
2.443
53.95
y
57.25
y
59.13
y
3.846
49.64
y
51.61
y
53.87
y
3.287
2 IU
52.06
y
49.55
y
48.97
y
3.002
4 IU
40.21b,y
57.94a,y
61.69a,y
3.316
Control
17.52y
18.08y
12.06y
2.443
46.05
x
42.75
x
40.87
x
3.846
50.36
x
48.39
x
46.13
x
3.287
2 IU
47.94
x
50.45
x
51.03
x
3.002
4 IU
59.79a,x
Total milk
(ml)
0.5 IU
Machine
milk (%)
1 IU
0.5 IU
Residual
1 IU
milk (%)
342
a–b
343
x–y
344
0.05).
345
1
42.06b,x
38.31b,x
3.316
Means with different superscripts within the same row are different (P < 0.05).
Means with different superscripts within the same column for each item are different (P <
Data are estimated marginal means and standard error of means.
346
347
348
349
350
351
352
15
119
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
353
Table 3. Milk composition of machine milk and residual milk of goats injected with different
354
doses of oxytocin at 4-h milking intervals.1
Milking time (h)
Parameter
Treatment
1200
1600
2000
SEM
Control
5.12a
4.22b
3.86b
0.125
5.02
a
4.00
b
3.64
b
0.139
5.21
a
4.33
b
3.78
b
0.223
2 IU
6.05
a
4.62
b
4.13
b
0.170
4 IU
5.58a
4.02b
3.71b
0.170
Control
5.19a
4.67ab
4.26b
0.129
4.83
a
3.95
b
4.00
b
0.131
5.78
a
4.07
b
4.38
b
0.195
2 IU
5.83
a
4.16
b
4.46
b
0.156
4 IU
5.55a
4.01b
4.18b
0.162
Control
2.87
2.98
2.81
0.075
Protein
0.5 IU
2.43
2.73
2.74
0.079
machine
1 IU
2.64
2.97
2.77
0.078
milk (%)
2 IU
2.73
2.91
3.07
0.075
4 IU
2.75
3.24
3.23
0.100
Control
3.16
3.41
3.40
0.112
Protein
0.5 IU
2.89
3.17
2.96
0.089
residual
1 IU
2.86
3.39
3.17
0.086
milk (%)
2 IU
3.04
3.45
3.19
0.097
4 IU
3.45
3.71
3.56
0.063
Control
4.48
4.55
4.59
0.029
Lactose
0.5 IU
4.45
4.68
4.62
0.057
machine
1 IU
4.52
4.68
4.73
0.042
milk (%)
2 IU
4.44
4.54
4.44
0.041
4 IU
4.50
4.41
4.45
0.045
Control
4.87
4.94
4.95
0.026
Lactose
0.5 IU
4.79
4.89
4.91
0.036
residual
1 IU
4.88
4.93
4.94
0.036
milk (%)
2 IU
4.83
4.89
4.94
0.032
4 IU
4.66
4.78
4.77
0.030
0.5 IU
Fat machine
milk (%)
1 IU
0.5 IU
Fat residual
milk (%)
355
a–c
356
1
1 IU
Means with different superscripts within the same row are different (P < 0.05).
Data are estimated marginal means and standard error of means.
16
120
MANUSCRITO 4
357
Table 4. Milk yield, milk composition, and SCC of goats before (Day 0) and after (Day 1–3)
358
injecting different doses of oxytocin at 4-h milking intervals.1
Days
Treatment
0
1
2
3
Control
1.49a
0.95b
1.57a
1.55a
0.097
1.85
a
0.97
b
1.77
a
1.75
a
0.054
1.53
a
0.96
b
1.60
a
1.55
a
0.042
2 IU
1.72
a
0.97
b
1.73
a
1.65
a
0.077
4 IU
1.81a
0.98b
1.85a
1.73a
0.067
Control
4.17a
3.71b
3.24c,x
4.07ab
0.084
3.80
a
3.34
b
3.15
c,x
3.82
a
0.108
4.24
a
3.45
b
2.67
c,y
3.98
a
0.183
2 IU
4.37
a
3.73
b
2.70
c,y
ab
0.173
4 IU
4.25a
3.32b
2.65c,y
3.95a
0.221
Control
2.86b
3.31a
3.31a,y
3.16ab,y
0.059
2.58
c
ab
3.28
a,y
bc,y
0.072
2.78
c
3.50
a,y
b,y
0.127
2 IU
2.77
c
ab,xy
0.148
4 IU
3.05c
3.53b
3.82a,x
3.77ab,x
0.137
Control
4.56
4.69
4.75
4.79
0.042
0.5 IU
4.66
4.77
4.76
4.69
0.026
1 IU
4.71
4.81
4.88
4.88
0.022
2 IU
4.61
4.79
4.88
4.81
0.040
4 IU
4.59
4.64
4.65
4.62
0.035
Control
6.25a,x
6.15a,x
5.88b,x
5.88b,y
0.035
0.5 IU
Milk yield
(L/d)
1 IU
0.5 IU
Fat (%)
1 IU
0.5 IU
Protein (%)
Lactose (%)
1 IU
6.24
x
5.42
y
2 IU
6.16
x
4 IU
6.20x
0.5 IU
SCC (log/ml)
359
a–c
360
x–y
361
0.05).
362
1
1 IU
3.23
3.24
b
3.25
b
6.31
x
5.68
y
6.51
x
6.28x
3.57
a,xy
6.14
x
5.39
y
6.00
x
5.91x
SEM
3.93
2.87
3.18
3.37
x
0.050
z
0.054
xy
0.039
6.10xy
0.045
6.33
5.34
6.05
Means with different superscripts within the same row are different (P < 0.05).
Means with different superscripts within the same column for each item are different (P <
Data are estimated marginal means and standard error of means.
363
17
121
MANUSCRITO 5
MANUSCRITO 5
Study of mammary tight junction permeability in dairy goats traditionally milked
once a day
A. Torresa, N. Castrob, A. Suárez-Trujillob, A. Argüellob, and J. Capotea*
a
Instituto Canario de Investigaciones Agrarias (ICIA), La Laguna 38200, Tenerife,
Spain
b
Department of Animal Science, Universidad de Las Palmas de Gran Canaria, Arucas
35413, Spain.
*
Corresponding author: Juan Capote, ICIA, Apto. de correos 60, La Laguna 38200,
Tenerife, Spain.
Tel.: +34 922542800; fax: +34 922542898. E-mail address: [email protected]
ABSTRACT
Effects of milking interval on mammary tight junction permeability are welldocumented in ruminants. However, the most studies have been focused in animals that
usually are milked twice a day. For this reason, thirty-two dairy goats in mid lactation of
two breeds traditionally milked once a day (Majorera, Palmera) and two parity numbers
(primiparous, multiparous) were used to evaluate the short-term effects of different
milking intervals (10, 14, 24, 28, and 32 h) on tight junction permeability of mammary
epithelia. Milk samples were analyzed for determination of chemical composition, and
Na and K concentrations. Blood samples were immediately taken after each milking and
analyzed for determination of lactose, and Na and K concentrations. Milk volumes
increased when milking interval was increased. On average, it increased from 2.23 to
2.73 L in Majorera, and from 1.38 L to 1.63 L in Palmera goats, at 24- and 32-h of milk
accumulation, respectively, which demonstrated the adaptation of the studied breeds to
accommodate greater milk volumes into the udder at extended milkings. Furthermore, it
125
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
did not produce apparent changes in the milk composition from 24- to 28-h, and from
24- to 32-h intervals. The concentrations of Na and K in milk and blood did not reflect
the degree of permeability of tight junctions at extended milkings, at least in goats
traditionally milked once a day. Finally, plasma lactose increased sharply at 24-h, being
more pronounced in primiparous (from 65.59 to 111.81 μM, at 14- and 24-h,
respectively) than multiparous goats (from 161.67 to 241.95 μM, at 14- and 24-h,
respectively), indicative of an increase in the permeability of tight junctions.
1. Introduction
Tight junctions form the continuous intercellular barrier between epithelial cells,
which is required to separate tissue spaces and regulate selective movement of small
molecules and ions across the epithelium (Anderson and Van Itallie, 2009). In the
mammary gland, the tight junctions are dynamic structures between the blood, or more
precisely the interstitial fluid (basolateral side), and milk in the alveolar lumen (apical
side), thus preventing serum components from entering into milk and vice versa
(Stelwagen et al., 1995). In addition, tight junctions are instrumental in maintaining the
polarized state of secretory cells, and keeping a difference in lipid and protein
composition between the basal and apical side of the plasma membrane (Stelwagen et
al., 1998).
In the mammary epithelium, tight junctions are formed during lactogenesis, prior
to onset of copious milk secretion, and are leaky during mammary involution (Nguyen
and Neville, 1998; Ben Chedly et al., 2010). During lactation the tight junctions are
become impermeable in most lactating animals, including ruminants. However,
systemic and local factors, such as changing hormone concentration, intramammary
pressure and mastitis, have been shown to regulate tight junction permeability
126
MANUSCRITO 5
(Stelwagen et al., 1999b). Tight junctions switch to a leaky state after approximately 18
h of milk accumulation in cows (Stelwagen et al., 1997), after 20 h in sheep (Castillo et
al., 2008), and after 21 h in goats (Stelwagen et al., 1994). Moreover, Stelwagen et al.
(1994) have previously shown that a decrease in the rate of milk secretion is correlated
with the leakiness of mammary tight junctions observed during extended milking.
However, Ben Chedly et al. (2013) found that the decrease in milk yield that occurs
during once daily milking in goats is due to regulation of synthetic activity rather than
to apoptosis of mammary epithelial cells or the state of the mammary gland tight
junctions.
The Na and K balance between the alveolar lumen and the interstitial fluid is
conditioned by tight junction integrity. Thus, Na and K can freely cross the apical
membrane, and the changes in the concentrations of these ions lead to corresponding
intracellular changes (Stelwagen et al., 1999a). Furthermore, lactose is a component
synthesized only in the mammary gland and is not secreted basolaterally in significant
quantities, so its presence in blood can only be explained by its movement from milk
into blood via leaky tight junctions (Stelwagen et al., 1994; Castillo et al., 2008).
Knowledge about how different milking intervals affect the permeability of tight
junctions in dairy goats traditionally milked once a day is required. For this reason, the
objective of this study was to evaluate some indicators of leakiness of tight junction at
different milking intervals in two dairy goat breeds traditionally milked once a day.
2. Material and methods
The experimental animal procedures were approved by the Ethical Committee of
the Universidad de Las Palmas de Gran Canaria (Arucas, Spain). The present study was
performed in the experimental farm of the Instituto Canario de Investigaciones Agrarias
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
(Tenerife, Spain) on 32 dairy goats belonging to two breeds: Majorera (n = 8,
primiparous, 2.09 ± 0.53 L/d; n = 8; multiparous, 2.11 ± 0.57 L/d), and Palmera (n = 8,
primiparous, 1.35 ± 0.39 L/d; n = 8; multiparous, 1.41 ± 0.20 L/d), in mid lactation at
the beginning of the experiment. The animals were fed according to the guidelines of
the Institute National de la Recherche Agronomique (INRA, Paris, France) and
recommendations (Jarrige, 1990). The goats were divided in 2 flocks (n = 16) balanced
for parity (primiparous and multiparous) and breed (Majorera and Palmera) with similar
milk yields.
The experiment considered 4 milking intervals (Flock 1: 10, 14, 24, and 28 h;
Flock 2: 10, 14, 24, and 32 h), where milk and blood samples were taken for analysis.
Goats were milked in a double 12-stall parallel milking parlor (Alfa-Laval, Madrid,
Spain) equipped with recording jars (4 L ± 5%) and a low-line milk pipeline. Milking
was performed at a vacuum pressure of 42 kPa, a pulsation rate of 90 pulses/min, and a
pulsation ratio of 60/40 in accordance with Capote et al. (2006). The milking routine
included wiping dirt off teat ends and stripping 2-3 squirts of milk from each teat,
machine milking and stripping milking, done by the operator to remove the milk
remaining in the udder before cluster removal, and teat dipping in an iodine solution
(P3-cide plus, Henkel Hygiene, Barcelona, Spain).
Milk volumes were recorded by using the recording jars in the milking parlor.
Milk samples were analyzed for determination of chemical composition, and Na and K
concentrations. Blood samples were immediately taken after each milking and analyzed
for determination of lactose, and Na and K concentrations. Milk fat, protein and lactose
percentages were determined by using a DMA2001 Milk Analyzer (Miris Inc., Uppsala,
Sweden). Concentrations of Na and K in milk were determined using atomic absorption
spectrometry (AAnalyst 200 spectrometer, Perkin-Elmer, Norwalk, USA) in the
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MANUSCRITO 5
Laboratory of Chemical Analysis of the Instituto Canario de Investigaciones Agrarias,
and the concentrations of these ions in blood were measured by means of ion selective
electrodes (Olympus AU2700 analyzer, Beckman Coulter, Tokyo, Japan) in the
Laboratory LGS Análisis. The enzymatic assay for determination of plasma lactose
(Boehringer Mannheim / R-Biopharm) was based on two reactions, one measuring
galactose and the other measuring lactose and galactose; the difference between the two
provided a measurement of lactose concentration. This analysis was conducted in the
Laboratory of Research Unit at University Hospital (Tenerife, Spain).
The statistical analyses were performed by using SPSS 15.0 software (SPSS
Inc., Chicago, USA). Repeated measures analysis of variance (ANOVA), with
adjustments for non-sphericity (Greenhouse-Geisser correction), was applied to evaluate
milking intervals effects on studied parameters; followed by LSD post-hoc tests.
Differences among experimental groups (Majorera-primiparous, Majorera-multiparous,
Palmera-primiparous,
Palmera-multiparous)
were
evaluated
using
a
multiple
comparison test following the Tukey method. Statistical differences were considered
significant at P < 0.05. Data are presented as least squares means.
3. Results
Milk volume (Table 1) was affected due to milking interval in both experimental
flocks (P < 0.05). However, Majorera and Palmera goats did not show differences from
10- to 14-h of milk accumulation, but a significant increase was observed from 14- to
24-h intervals in the studied groups. In the Flock 1, milk volume at 28-h was higher
than milk volume at 24-h in the studied breeds, but these differences were not
significant (P > 0.05). In contrast, the goats of Flock 2 showed a dramatic increase in
milk volume in Majorera primiparous (17%), Majorera multiparous (27%), Palmera
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
primiparous (20%), and Palmera multiparous (10%) from 24- to 32-h of milk
accumulation. Regarding breed effect, no significant differences were found between
Majorera and Palmera goats at 10-h milking interval. Nevertheless, Majorera goats had
higher milk volumes than Palmera goats at subsequent milking intervals (P < 0.05).
Additionally, milk volumes were similar (P > 0.05) between primiparous and
multiparous goat at different milking intervals.
Milk fat percentages (Table 1) were comparable between consecutive milking
intervals (P > 0.05), except for goats of the Flock 1, where milk at 14-h contained lower
percentages of fat than milk at 24-h (P < 0.05). Nevertheless, there was a trend to obtain
milk richer in fat content when the milking intervals differ by more than 14 hours (P <
0.05). In addition, fat percentage was not affected by breed and parity factors, both in
goats of Flock 1 and 2 (P > 0.05).
No significant differences were detected in milk protein percentages from 10- to
14-h milking intervals in the studied groups (Table 1). Subsequently, Majorera breed
had an increase in protein content when interval switched from 14- to 24-h (P < 0.05),
and stayed stable from 24- to 28- and 32-h (P > 0.05). Likewise, Palmera goats did not
have differences in protein content from 24- to 28- and 32-h. Breed and parity had not
effects on milk protein percentage at the studied milking intervals.
No differences were found in milk lactose percentages in the studied goats
(Table 1) when the milking interval and breed factors were considered (P > 0.05).
Regarding parity effect, Palmera primiparous had higher values than Palmera
multiparous at 28- and 32-h (P < 0.05). However, these differences were not significant
between Majorera primiparous and multiparous.
Milking interval did not modify Na content in milk for Majorera goats (Table 2).
Only a slight increase in Na concentration was observed for Palmera primiparous and
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MANUSCRITO 5
multiparous (Flock 2) from 10- with respect to 24- and 32-h. In general, primiparous
goats had lower levels of Na than multiparous goats, whereas Palmera had higher values
than Majorera of these ions in milk, when the parity and breed effects were considered,
respectively. Moreover, no changes were found in concentration of K in milk for the
goat groups due to milking interval, breed or parity factors (P > 0.05).
Goat breed and parity did not affect (P > 0.05) Na and K concentration in
plasma blood at all intervals (Table 2). Besides, as milking interval increased,
concentration of Na in blood plasma decreased for Majorera and Palmera in both
parities (P < 0.05). Otherwise, concentration of K in blood plasma was steady until 28-h
(Flock 1) and increased markedly at 32-h (Flock 2) for all goat groups.
Milking interval affected (P < 0.05) lactose concentration in plasma (Table 2). It
was observed that after 14-h interval, Majorera and Palmera goats in both parities
dramatically increased its levels of lactose in plasma blood. Likewise, parity factor had
an effect on plasma lactose, where primiparous goats exhibited lower values than
multiparous goats at the studied milking intervals. Finally, no differences were observed
between Majorera and Palmera breeds at the different intervals (P > 0.05).
4. Discussion
The increases in milk volume with increasing milking intervals, is a
consequence of a wider cisternal capacity of the studied breeds, which allowed a
continuous drop of milk from alveoli to the cistern, reducing the feedback inhibitor
process, the alveolar milk stasis and alveolar pressure (McKusick et al., 2002; Torres et
al., 2013a). Typically in goats, 24-h of milk stasis is necessary to activate regulatory
mechanisms leading to disruption of tight junctions and reduced milk secretion, longer
than the 18 h required to induce a similar phenomena in cows and sheep (Marnet and
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Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Komara, 2008). Goats have a higher proportion of milk in their cistern than ewes or
cows, which most likely contributes to their ability to better maintain milk yield under
extended milking (Silanikove et al., 2010).
Disruption of mammary tight junctions is associated with a decrease in milk
yield due to longer milking intervals (Stelwagen et al., 1994; Delamaire and GuinardFlament, 2006), which is related with cell death and a decrease in mammary activity
(Ben Chedly et al., 2010). It is predicted that for milking intervals of less than 20-h in
goats and 18-h in cows, the concentration of β-casein f(1–28), peptide that serves as a
local regulator on milk secretion, would be higher in the cistern than in the alveoli
(Silanikove et al., 2000). Therefore, the alveoli will not be exposed to the full impact of
the negative feedback signal of this peptide. Extending milk stasis beyond these times
exceeds the storage capacity of the cistern, resulting in the equilibration of β-casein f(1–
28) concentration between the cistern and the alveoli, and inducing disruption of the
tight junction (Silanikove et al., 2010).
The higher volume of milk found for Majorera goats compared with Palmera
goats is due to cisternal size of each breed. Previously, Torres et al. (2013a) reported
that Majorera have higher udder depth values (difference in distance between the udder
floor and the cistern floor) than Palmera, which is correlated with the udder volume
(Capote et al., 2006). Bruckmaier et al. (1997) explained that a large absolute cisternal
volume implies that a large fraction of the milk is stored within the cisternal cavities.
Castillo et al. (2008) showed a greater milk accumulation rate in Lacaune than in
Manchega ewes, where Lacaune breed have a greater cisternal area than Manchega
breed (Rovai et al., 2008).
Milk volume in multiparous goats was higher than primiparous goats, but the
statistical differences were no significant, which was unexpected. Goetsch et al. (2011)
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MANUSCRITO 5
reported that milk production is lower for primiparous than for multiparous dairy goats.
Salama et al. (2004) found that the differences in storage capacity of the cisterns
between primiparous and multiparous goats were more evident after 24 h of milk
accumulation, in which multiparous goats had larger cisternal area and were able to
store more volume of milk in the cistern than primiparous goats. McKusick (2000)
found that ewes with high milk volume-intramammary pressure ratio had a significant
degree of compliance in their udders because they were able to accommodate an
increase in intramammary pressure of 30% when the milking interval was extended to
24 h. Therefore, intramammary compliance or elasticity plays a significant role to
accommodate the milk volumes secreted. The results obtained could be explained by the
fact that primiparous goats had an optimal intramammary compliance due to adaptation
of the breed to once daily milking. However, further studies are needed to verify this
hypothesis.
Milk fat percentages had a trend to be higher as milking interval increased.
However, McKusick et al. (2002) and Castillo et al. (2008) in ewes, and Ayadi et al.
(2004) in cows observed that milk fat content decreased with longer milking intervals.
These authors indicate that there was transfer of milk fat from the alveoli to the cistern
during early udder filling, but this transfer was no longer taking place during the later
intervals. It has been reported an upward movement of the fat globules, in the opposite
direction to the downward draining and newly secreted milk at extended milking in
dairy cows (Ayadi et al., 2004). Conversely, this cistern recoil phenomenon did not
occur in goats, where once milk is ejected, it is unable to return to the alveoli (Salama et
al., 2004). In addition, Komara et al. (2009) in Alpine goats and Torres et al. (2013b) in
Majorera and Palmera goats did not find differences in fat percentages between once
and twice daily milking. Moreover, according to Stelwagen et al. (1997), the diameter
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y parámetros de calidad de la leche en las cabras canarias
of milk fat globules is greater than the intercellular joints, and Komara et al. (2009)
found that fat globule size between once and twice daily milking were similar for dairy
goats. Therefore, changes in fat content according to milking interval are related to the
regulatory mechanisms for secretion of large and high-viscosity milk fat globules
relative to the components in the aqueous phase of milk (Davis et al., 1999).
Milk protein percentages did not have changes at extended milking in the
studied breeds, which agrees with observations in dairy cows by Ayadi et al. (2004) and
dairy ewes by Castillo et al. (2008), where protein content in milk was constant after 12
h. However, McKusick et al. (2002) found an increase in milk protein fraction from 20
h in dairy ewes. The tendency of protein content to increase for extended milking
intervals in some species or breeds may be explained by increased tight junction
leakiness allowing serum protein entering into the milk, since casein does not move
through leaky mammary tight junction (Ayadi et al., 2004; Castillo et al., 2008).
However, typical milk albumin concentration (the greatest potential contributor of
serum protein to milk) is too small to make an effect on protein concentration in milk,
being produced and secreted by mammary epithelial cells into milk (Silanikove et al.,
2013). Therefore, the changes in milk protein content according to milking interval, like
milk fat content, seems are more correlated to regulation of synthetic activity of
secretory cells or hydrolysis of protein rather to disruption of the mammary gland tight
junctions (Ben Chedly et al., 2013).
The absence of differences in milk lactose percentages found in the studied goats
according to milking interval factor is related with the udder size. Thus, Castillo et al.
(2008) reported a decrease in lactose content from the 20- to 24-h milking interval in
Manchega ewes (small udder cisterns), but not in Lacaune ewes (large udder cisterns).
Decreases of milk lactose percentage seem to be due to lactose passing from milk into
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MANUSCRITO 5
blood through impaired tight junctions associated with extended milking intervals
(Stelwagen et al., 1994). However, Ben Chedly et al. (2013) proposed that the reduction
of milk lactose yield is essentially due to a reduction of its synthesis by the mammary
gland.
In general, Na and K contents in milk were not affected by the studied milking
intervals. Only a slight increase was observed in Na content for Palmera goats from 10to 24- and 32 intervals. When the permeability of tight junctions increases, the
concentration of Na in milk increases, and the concentration of K decreases (Stelwagen
et al., 1999a). Furthermore, a reduction of Na content and an increase of K content in
blood plasma would be expected during the disruption of tight junctions. In the present
experiment was detected the diminution of Na values in blood plasma in the studied
groups when the milking interval was increased, and the concentration of K only was
increased both Majorera and Palmera goats at 32-h interval. Castillo et al. (2008) did
not find differences in Na and K concentration in milk in Lacaune ewes at extended
milking intervals, but Manchega ewes had an increase of Na and a decreased of K in
milk after 20 h. These authors suggested that variations in ion concentration have a
relationship with the adaptation to extended milking intervals of these breeds being
lower in Manchega than Lacaune ewes. Furthermore, Stelwagen et al. (1994) found that
Na concentration in milk increased from 16.3 mM at 0 h to 21.3 mM at 36 h, and the K
concentration in milk decreased from 46.7 mM at 0 h to 34.3 mM at 36 h in Saanen
goats, as consequence of tight junction disruption. In the present study, Majorera and
Palmera breeds are fully adapted to once daily milking, which can explain that
concentrations of Na and K were not the best indicators of leakiness of tight junctions.
Despite the high variability of plasma lactose concentration obtained in the
experimental groups, this increased sharply at 24-h, indicative of an increase in tight
135
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
junction permeability. Castillo et al. (2008) considered that lactose in plasma is the main
indicator of mammary tight junction permeability, because changes in Na and K
concentrations may reflect an alteration in the transport of these ions across transcellular
rather than paracellular pathways. In Saanen goats, Stelwagen et al. (1994) showed an
increase of plasma lactose concentration after 21 h of milk accumulation, whereas that
in dairy cows, Stelwagen et al. (1997) observed the increase of lactose in plasma after
18 h of milk stasis. In addition, some studies which switched from twice to once daily
milking in goats and cows (Stelwagen et al., 1997; Ben Chedly et al., 2013)
demonstrated that the increase in blood lactose concentration is transient, suggesting
that the gland gradually adapted to once daily milking. Finally, the increases of plasma
lactose seem to have not been conditioned by breed effect. Nevertheless, primiparous
goats had an increase more pronounced in plasma lactose values than multiparous goats
at extended milking intervals, although these animals presented the highest
concentrations, which may indicate that the older animals had a greater degradation in
the integrity of tight junction due to different lactations. On the other hand, Castillo et
al. (2008) found that Manchega ewes increased by 5-fold its plasma lactose values from
20- to 24-h, whereas Lacaune ewes increased by only 1.5-fold, indicating that the tight
junction leakiness effect was greater in Manchega that in Lacaune ewes. Therefore, the
udder development plays an important role on degree of tight junction leakiness.
5. Conclusions
The wide cisternal capacity of the Majorera and Palmera breeds allowed an
increase in milk yield above to 24 h of milk accumulation. Furthermore, milk
composition was not impaired when milking intervals were increased until 28 or 32 h.
In regard to indicators of leakiness of tight junction, the concentrations of Na and K in
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MANUSCRITO 5
milk and blood did not reflect its degree of permeability, at least in goats traditionally
milked once a day. Moreover, the increase in the concentration of plasma lactose after
14 h did not allow to precise whether the disruption of tight junctions occurred before or
after to 24 h, or simply is normal flux of lactose from apical to basolateral side due to
status of tight junctions in goats usually milked once time a day. Therefore, a milking
interval between 14- and 24-h will be necessary to take into consideration to evaluate
the integrity of tight junctions. Nevertheless, the results did not show a clear
relationship between the milk yields and damages of tight junction permeability, which
is interesting to develop breeding programs adapted to extended milkings, in areas that
require it.
Conflict of interest
None.
Acknowledgments
This work was supported by Fondo Europeo de Desarrollo Regional-Instituto
Nacional de Investigación y Tecnología Agraria y Alimentaria (FEDER-INIA)
RTA2009-00125. The authors are also grateful to Dr. Eduardo Salido and Dr. Ana Rosa
Socorro for their assistance with the experimental procedures.
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Table 1. Effects of milking interval on milk volume and milk composition in two dairy
goat breeds 1
Flock 1
Flock 2
Milking interval (h)
Milking interval (h)
SEM
10
14
24
28
Majorera primiparous
1.02a
1.40a,y
1.81b,y
2.05b,y
Majorera multiparous
1.04
a
1.31
a,y
2.03
b,y
2.18
b,y
0.61
a
0.71
a,x
1.11
b,x
1.35
b,x
0.72
a
SEM
10
14
24
32
0.157
0.98a
1.31a,xy
2.23b,y
2.61c,y
0.208
0.176
1.21
a
1.50
a,y
2.24
b,y
2.84
c,y
0.198
0.64
a
0.80
a,x
1.20
b,x
1.44
c,x
0.128
0.116
0.72
a
1.55
b,x
1.71
c,x
0.108
0.189
2.27a
2.25a
2.83ab
3.05b
0.113
a
a
ab
b
0.118
Milk volume (L)
Palmera primiparous
Palmera multiparous
1.03
a,xy
1.45
b,xy
1.76
c,xy
0.155
1.00
a,xy
Milk composition
Fat (%)
Majorera primiparous
2.17a
2.55a
3.15b
3.66b
Majorera multiparous
2.95
a
a
b
b
0.187
2.99
Palmera primiparous
2.41a
2.45a
3.72b
3.56b
0.225
2.69a
2.88ab
3.64b
3.37b
0.134
Palmera multiparous
2.43ª
3.03a
3.92b
4.22b
0.207
2.39a
2.95ab
3.51bc
3.83c
0.173
Majorera primiparous
2.39a
2.73a
3.19b
3.39b
0.156
2.19a
2.38a
3.03b
3.02b
0.118
Majorera multiparous
2.89a
2.89a
3.84b
4.30b
0.205
2.49a
2.75a
3.08b
3.40b
0.142
Palmera primiparous
2.37a
3.01ab
3.73b
3.54b
0.176
2.32a
2.82ab
3.19bc
3.73c
0.173
Palmera multiparous
a
3.07
a
3.98
b
b
0.180
2.41
a
ab
bc
c
0.165
5.06
4.95
4.73
4.69xy
0.124
5.51
5.05
5.08xy
0.085
4.55
4.38
x
4.83
4.75
x
0.109
y
0.070
5.35
5.17
5.06
5.22
y
0.087
0.136
4.94
5.04
4.77
4.80x
0.098
3.24
4.11
4.38
2.89
3.19
3.61
Protein (%)
2.97
4.01
3.04
3.36
3.87
Lactose (%)
Majorera primiparous
Majorera multiparous
4.67
4.43
Palmera primiparous
5.33
5.08
4.76
5.03
Palmera multiparous
4.53
4.81
4.39
4.20x
a–c
4.98
5.09
Means with different superscripts within the same row are different (P < 0.05).
x–y
1
0.082
5.45
Means with different superscripts within the same column for each item are different (P < 0.05).
Data are least square means and standard error of means.
142
MANUSCRITO 5
Table 2. Effects of milking interval on concentration of Na and K in milk and plasma
blood and concentration of plasma lactose in two dairy goat breeds 1
Flock 1
Flock 2
Milking interval (h)
Milking interval (h)
SEM
SEM
10
14
24
28
10
14
24
32
Majorera primiparous
12.38x
13.47x
14.80x
14.99x
0.437
12.65x
14.13x
13.99x
13.33x
Majorera multiparous
18.62
y
y
xy
19.87
y
0.605
0.519
y
y
y
y
12.53
x
15.99
x
15.41
x
0.996
b,xy
19.76
y
22.36
y
22.17
y
24.36
z
0.880
b,y
0.763
0.620
Majorera primiparous
34.75
37.44
37.02
37.15
0.904
35.70
39.82
38.07
38.53
0.960
Majorera multiparous
36.01
38.80
42.80
39.96
1.149
38.13
41.99
40.98
40.24
0.728
Palmera primiparous
34.16
36.99
34.51
35.57
0.805
33.35
36.33
35.13
33.20
0.536
Palmera multiparous
33.36
35.76
37.44
34.02
1.131
34.65
36.32
37.93
36.44
0.839
Majorera primiparous
146.08b
145.55b
144.68a
144.23a
0.278
145.95b
145.30b
144.05a
143.90a
0.287
Majorera multiparous
148.53c
146.95bc
146.80ab
144.90a
0.517
146.88b
146.05ab
144.15a
144.45a
0.417
Palmera primiparous
146.45
b
144.85
ab
142.70
a
142.75
a
0.552
b
145.93
ab
143.85
a
a
0.455
147.05
b
145.20
ab
144.18
a
143.33
a
145.50
bc
143.80
a
ab
0.365
Milk
Na (mM)
Palmera primiparous
Palmera multiparous
17.43
14.36
xy
18.17
0.538
20.03
13.78
a,x
17.70
a,y
18.74
15.56
ab,xy
18.29
ab,y
21.99
16.51
20.87
b,x
b,xy
20.76
17.02
21.28
K (mM)
Plasma blood
Na (mM)
Palmera multiparous
147.28
c
143.80
0.464
147.00
144.40
0.120
5.10a
4.78a
4.73a
5.88b
0.148
ab
a
a
b
0.165
K (mM)
Majorera primiparous
5.18
5.08
5.00
5.73
Majorera multiparous
5.23
5.03
4.90
5.45
0.102
5.28
4.93
4.60
5.90
Palmera primiparous
5.33
5.05
4.95
5.53
0.134
5.03ab
4.90a
4.55a
5.45b
0.117
Palmera multiparous
4.93
5.10
4.88
5.63
0.136
4.68a
4.58a
4.43a
5.58b
0.134
54.96a,x
66.51a,x
127.85b,x
181.05c,y
14.435
65.48a,x
84.39b,xy
140.98c,x
230.23d,y
17.707
b,y
c,z
a,z
b,y
c,z
21.158
c,x
12.528
314.44c,z
22.815
Plasma lactose (μ M)
Majorera primiparous
Majorera multiparous
135.45
a,y
a,x
Palmera primiparous
44.26
Palmera multiparous
136.75a,y
177.23
56.26
a,y
a,x
160.35a,y
235.51
88.73
b,x
264.00b,y
328.22
20.651
120.64
a,y
c,x
10.100
43.28
342.21c,z
22.518
106.96a,y
110.38
a,x
180.95
55.18
a,x
128.15a,y
222.92
89.71
b,x
245.37b,y
308.96
152.78
a–d
Means with different superscripts within the same row are different (P < 0.05).
x–z
Means with different superscripts within the same column for each item are different (P < 0.05).
1
Data are least square means and standard error of means.
143
CONCLUSIONES
CONCLUSIONES
Artículo 1
El hecho de que alrededor del 80% de la leche total que se encuentra en la ubre, se almacene
en los compartimentos cisternales, tanto a las 14- como a las 24-h, sugiere que la mayor parte de la
transferencia de leche desde los alvéolos a la cisterna ocurre durante las primeras fases de llenado
de la glándula. Por esa razón no se encontraron diferencias, en relación a la composición química de
la leche cisternal, entre ambos intervalos de ordeño. Sin embargo, los diversos cambios que presentaron los contenidos de grasa, lactosa y sólidos totales en la leche alveolar, sugieren la necesidad de
posteriores estudios sobre los mecanismos responsables de la eyección de la leche entre ordeños.
Artículo 2
Los resultados demostraron que la práctica del doble ordeño no mejora la producción de
leche respecto a un ordeño diario en las cabras de raza Majorera y Tinerfeña, lo cual es de interés
para los sistemas de producción caprina, en donde se busca reducir los costes relacionados con la
producción de leche. No obstante, el aumento significativo en la producción lechera que mostraron
las cabras de raza Palmera al ordeñar dos veces al día, sugiere que podría ser una práctica rentable
en ciertos momentos de la lactación. Sin embargo, el contenido de proteína en leche no incrementó
en concordancia con la producción. Por esta razón, se necesitan otros estudios para evaluar los
efectos de la frecuencia sobre el rendimiento quesero, lo cual es un aspecto de suma importancia en
la economía ganadera de Canarias. Además, el conocimiento de las estructuras de fraccionamiento
de leche puede servir de base para futuros programas de selección, al objeto de mejorar la facilidad
de ordeño en las razas locales.
Manuscrito 3
Los cambios a corto plazo de la frecuencia normal de ordeño en cabras tradicionalmente ordeñadas una vez al día durante la lactancia temprana puede afectar la producción de leche en cabras
de raza Majorera, como lo demuestra el incremento significativo cuando se cambia de uno a dos ordeños diarios. Sin embargo, las variaciones en el contenido de grasa y perfil proteico requieren estudios acerca de cómo éstas afectan la producción y calidad de los quesos, ya que la finalidad principal
de las explotaciones caprinas canarias es la fabricación de ese producto. Por otro lado, la falta de
incremento en la producción durante el triple ordeño, con la disminución en los porcentajes de grasa
en la leche, hace necesario futuros estudios para evaluar las causas que provocan este descenso.
147
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero
y parámetros de calidad de la leche en las cabras canarias
Manuscrito 4
La liberación de oxitocina por estimulación previa al ordeño y la administración de oxitocina
sintética no tuvo efecto galactopoyético ni cambios aparentes en la composición química de la leche
en cabras no ordeñadas inmediatamente que tradicionalmente se ordeñaban una vez al día. Además,
la ausencia de diferencias en el fraccionamiento lechero y composición de la leche entre la administración de cuatro dosis de oxitocina indica que la contracción de las células mioepiteliales que
rodean los alvéolos es similar en respuesta a bajas y altas dosis de esta hormona.
Manuscrito 5
La amplia capacidad cisternal de las cabras de raza Majorera y Palmera permitió un aumento
de la producción de leche después de 24 h de acumulación. Además, la composición química de la
leche no se vio afectada cuando los intervalos de ordeño se incrementaron hasta 28 o 32 h. En lo que
se refiere a los indicadores de permeabilidad de las uniones celulares del epitelio mamario, las concentraciones de Na y K en leche y sangre no reflejaron un mayor grado de permeabilidad, al menos
en cabras tradicionalmente ordeñadas una vez al día. Por otra parte, el aumento en la concentración
de lactosa en el plasma sanguíneo, después de 14 h de acumulación de leche, no permitió precisar
si la rotura de las uniones celulares se produjo antes o después de 24 h, o se debía al flujo normal de
lactosa desde el lado apical al basolateral por el estado de dichas uniones en cabras acostumbradas
a largo intervalos de ordeño. Adicionalmente, los resultados no mostraron una relación entre los rendimientos de leche y daños en la permeabilidad de las uniones celulares, lo cual es interesante para
el desarrollo de programas de selección, en las zonas que requieran intervalos de ordeño más largos.
148