Reproduction and health in Holstein Warmblood mares

Transcription

Aus dem Institut für Tierzucht und Tierhaltung
der Christian-Albrechts-Universität zu Kiel
Reproduction and health in Holstein Warmblood mares
- Impact of population structure and data recording –
Dissertation
zur Erlangung des Doktorgrades
der Agrar- und Ernährungswissenschaftlichen Fakultät
der Christian-Albrechts-Universität zu Kiel
vorgelegt von
M.Sc. agr. Lukas Philipp Roos
aus Speyer, Rheinland-Pfalz
Dekan: Prof. Dr. E. Hartung
1. Berichterstatter: Prof. Dr. J. Krieter
2. Berichterstatter: Prof. Dr. G. Thaller
Tag der mündlichen Prüfung: 12. November 2014
Die Dissertation wurde mit dankenswerter finanzieller Unterstützung der
H. Wilhelm Schaumann Stiftung, Hamburg angefertigt
MEINEN ELTERN
TABLE OF CONTENTS
GENERAL INTRODUCTION…………………………………………………..
1
CHAPTER ONE
Inbreeding depression in horses: A review……………………………...…..
5
CHAPTER TWO
Investigations into genetic variability in Holstein horse breed
using pedigree data….…………………………………………………………
27
CHAPTER THREE
Effect of inbreeding on female fertility in Holstein horse breed…..………..
50
CHAPTER FOUR
Standardisierte Erfassung von Gesundheitsdaten beim
Holsteiner Pferd…….…………………………………………………………..
72
GENERAL DISCUSSION……………………………………………………..
96
GENERAL SUMMARY…….…………………………………………………..
104
ZUSAMMENFASSUNG…………………………………………………..…..
107
GENERAL INTRODUCTION
Reproductive performance and health are important key factors in equine breeding
and business (Dohms, 2002; Zent, 2003; Sairanen et al., 2009). Equine fertility is
known as a tangled functional trait with lots of influencing environmental and
management factors such as the age of the animal, the individual servicing at farm
level or the season. Thus, it is difficult to determine the fundamental factors directly
linked to the individuals (Mucha et al., 2012; Sairanen et al., 2009). Compared to
other livestock species, horses generally have lower fertility and are characterised by
a large generation interval (Mucha et al., 2012). Several risk factors such as various
kinds of fertility disorders could further complicate breeding activities.
Not only in horses inbreeding is known as a genetic factor that is capable of affecting
fertility,
depending
on
its
severity
(Charlesworth
and
Charlesworth,
1987;Charlesworth and Willis, 2009;Falconer and Mackay, 1996). Highly selected
and mostly line-bred populations with closed studbooks such as the Holstein horse
breed are more likely to produce closely related animals. Increased inbreeding
together with decreased effective population size maximise the risk of negative
effects on functional traits with low heritability (e.g. health and fertility) (Nomura et al.,
2001; Sierszchulski et al., 2005).
Besides high-quality pedigree information, consistently recorded phenotypes are
essential to estimate any kind of genetic and non-genetic effect on functional traits or
to establish new breeding strategies such as genomic selection. Standardised and
comprehensive data recording with a centrally managed database for health
phenotypes is currently not practiced in German horse breeding. A consistent key
system to manage, standardise and to analyse veterinary data is missing. Thus,
there is a lack of epidemiological knowledge needed to provide reasonable
1
emphases for selection with regard to health aspects (Sarnowski, 2013). The
implication of equine health into breeding schemes, focused on the estimation of
breeding values and the implementation of genomic selection, is currently limited by
using indirect traits such as conformation and performance (Koenen et al., 2004).
In Chapter One of this thesis, a review is presented of the current knowledge of the
occurrence and the estimation of inbreeding depression in horses. The objective was
to represent a general overview of the extent to which different kinds of traits (fertility,
morphology, pathological findings and performance) are affected by the population
structure of several horse breeds.
Against the background of traditional breeding policies with closed studbooks and
restricted licensing of foreign stallions, Chapter Two especially deals with the
population structure of Holstein Warmblood horses. The aim was to point out updated
levels of inbreeding, the proportions of foreign blood and to specify the genetic
contributions of outstanding founders to the current structure of the breeding stock.
Additionally, some alternative concepts regarding the evolution of inbreeding were
applied. According to the fact that increased inbreeding is able to affect fitnessassociated traits in a negative way, Chapter Three investigated the possible impacts
of inbreeding and other relevant factors (age effect) on fertility (foaling rate) and the
occurrence of fertility disorders (stillbirth) in Holstein Warmblood horses. Building on
this, any kind of research into genetic or non-genetic impacts on functional traits
necessarily depends on standardised and consistent phenotypic data. Inconsistent
phenotypes potentially skewed statistical analysis. Therefore, the aim of Chapter
Four was the initial development of a standardised monitoring system for centralised
equine health and fertility data recording. An attempt was made to acquire clinical
data, using a sample of selected breeding facilities in Schleswig–Holstein, together
2
with their caring veterinarians. The final aspect of this study was the development of
a consistent key system to categorise and standardise veterinary field data.
References
Charlesworth, D., and B. Charlesworth. 1987. Inbreeding Depression and its
Evolutionary Consequences. Annu. Rev. Ecol. Syst. 18(1):237–268.
doi:10.1146/annurev.es.18.110187.001321.
Charlesworth, D., and J. H. Willis. 2009. The genetics of inbreeding depression. Nat
Rev Genet 10(11):783–796. doi:10.1038/nrg2664.
Dohms, T. 2002. Einfluss von genetischen und umweltbedingten Faktoren auf die
Fruchtbarkeit von Stuten und Hengsten. Wissenschaftliche Publikation //
Deutsche Reiterliche Vereinigung 25. FN-Verl. der Dt. Reiterlichen Vereinigung,
Warendorf.
Falconer, D. S., and Mackay, Trudy F. C. 1996.Introduction to quantitative
genetics.4th ed. Longman, Essex, England.
Koenen, E., L. Aldridge, and J. Philipsson. 2004. An overview of breeding objectives
for warmblood sport horses. Livestock Production Science 88(1-2):77–84.
doi:10.1016/j.livprodsci.2003.10.011.
Mucha, S., A. Wolc, and T. Szwaczkowski. 2012. Bayesian and REML analysis of
twinning and fertility in Thoroughbred horses. Livestock Science 144(1):82–88.
Nomura, T., T. Honda, and F. Mukai. 2001. Inbreeding and effective population size
of Japanese Black cattle. J. Anim. Sci. 79(2):366–370.
Sairanen, J., K. Nivola, T. Katila, A.-M.Virtala, and M. Ojala. 2009. Effects of
inbreeding and other genetic components on equine fertility. Animal 3(12):1662.
doi:10.1017/S1751731109990553.
3
Sarnowski, S., Stock, K. F., Kalm, E.,Reents, R. 2013. Aufbau einer
Gesundheitsdatenbank für Pferde. 7. Pferde-Workshop Uelzen, 17th and 18th of
september 2014:108–117.
Sierszchulski, J., M. Helak, A. Wolc, T. Szwaczkowski, and W. Schlote. 2005.
Inbreeding rate and its effect on three body conformation traits in Arab mares.
Animal Science Papers and Reports 23(1):51–59.
Zent, W. 2003. Foal Heat-Breeding. In: Current Therapy in Equine Medicine.
Elsevier. p. 248–250.
4
CHAPTER ONE
Inbreeding depression in horses: A review
L. Roos and J. Krieter
Institute of Animal Breeding and Husbandry, Christian-Albrechts-University, Kiel, Germany
5
Abstract
In livestock production, the phenomenon of inbreeding depression is known as the
decreasing mean phenotypic performance in related individual’s progeny and is
caused by a reduction in homozygosity. This special kind of genetic change is more
likely to occur in traits related to fertility and fitness. For other livestock species, it is
considered proven that morphological traits are less sensitive to inbreeding
depression because of weakly pronounced dominant gene effects. In commercial
horse breeding facilities, depressed fitness-related traits or the increased volume of
fertility disorders as well as unfavourable morphological development could lead to
considerable economic loss. Against this background, the objective of this review
article was to give an overview of today’s knowledge of the occurrence and
estimation of the extent of inbreeding depression in various horse breeding traits
(fertility, morphology, pathological findings and racing performance). Inconsistent
findings indicate that, also in horses, fitness-associated traits such as reproductive
performance and fertility disorders as well as morphological traits are affected by
inbreeding depression. Depending on the structure, quality and depth of the pedigree
information, fluctuations were observed in the extent of inbreeding and its impact on
the traits analysed when compared in different studies.
6
Introduction
Deleterious effects of inbreeding have long been recognised in domesticated species
(Darwin, 1868). Inbreeding depression is widely known as the reduction of mean
phenotypic
performance
in
related
individual’s
progeny
(Charlesworth
and
Charlesworth, 1987; Charlesworth and Willis, 2009; Falconer and Mackay, 1996). It is
more likely to occur in traits related to reproduction and fitness (Charlesworth and
Charlesworth, 1987; Falconer and Mackay, 1996; Hansson and Westerberg, 2002).
Morphological traits are less sensitive to this kind of genetic change because of
weakly pronounced dominant gene effects (Falconer and Mackay, 1996; Fioretti et
al., 2002; Van Eldik et al., 2006; Van Wyk et al., 2009). Generally, inbreeding
depression is caused by increased homozygosity in individuals (Falconer and
Mackay, 1996; Charlesworth and Willis, 2009). The genetic basis for the loss of
heterozygosity is explained by two main hypotheses. First, the partial dominance
hypothesis (Davenport, 1908), in which inbreeding depression is caused by the
expression of deleterious recessive alleles in the homozygous state. Inbreeding
increases the frequency of homozygotes and deleterious recessive alleles become
increasingly expressed (Charlesworth and Willis, 2009). The second hypothesis,
known as the overdominance hypothesis (East, 1908; Shull, 1908), attributes
inbreeding depression to the advantages of heterozygotes over both homozygotes.
With an increase in homozygosity, the expression of overdominance is reduced by
the minored frequency of heterozygotes (Charlesworth and Willis, 2009). Additionally,
a third hypothesis by Templeton and Read (1994) partly explains inbreeding
depression as a consequence of a breakdown of epistatic interaction between loci
(Köck et al., 2009). Especially in horse breeding, depressed fitness-related traits such
as fertility could lead to considerable economic loss (Sairanen et al., 2009; Mucha et
al., 2012).
7
Compared to other livestock species, horses have lower fertility, characterised by a
large generation interval (Cothran et al., 1984; Mucha et al., 2012).
The aim of this review was to give an overview of today’s knowledge on the
occurrence and extent of inbreeding depression in various traits in horse breeding.
After describing methods to estimate inbreeding depression in horses, the results of
different studies are presented. The majority of the reviewed research papers
investigated inbreeding effects on reproductive performance and fertility disorders in
mares. Additionally, the results of scientific projects working on the impact of
inbreeding on male reproduction and on morphological traits are scoped in this
review article.
Methods to estimate inbreeding depression
Generally, two different ways to estimate inbreeding depression are distinguished
(Charlesworth and Willis, 2009). The direct way uses pedigree information to analyse
the relationship between trait values and inbreeding coefficients (e.g. Cothran et al.,
1984; Sierszchulski et al., 2005; Gómez et al., 2009; Sairanen et al., 2009). Another
direct approach is the experimental creation of individuals with various inbreeding
coefficients, using different kinds of mating schemes (e.g. Ehiobu et al., 1989;
Hinrichs et al., 2007; Moss et al., 2008). An indirect solution to detect inbreeding
depression is the use of inbreeding coefficients estimated from frequencies of
homozygotes and heterozygotes of genomic markers or SNPs (Curik et al., 2003).
For all of the stated methodologies, the estimated quantity could be described as
“inbreeding load” (Charlesworth and Willis, 2009).
In most of the studies dealing with the effect of inbreeding in horses, direct methods,
regressing pedigree-based inbreeding coefficients are used on various fertility,
conformation or performance traits (Cothran et al., 1984; Klemetsdal and Johnson,
8
1989; Klemetsdal, 1998; Sevinga et al., 2004; Langlois and Blouin, 2004). A minority
of research projects on horse breeding worked with SNP-data (e.g. Curik et al., 2003;
Binns et al., 2012).
The most common measures to quantify the inbreeding load of a subset of animals
are the inbreeding coefficient F of an individual i (Fi, e.g. Cothran et al., 1984; Dolvik
and Klemetsdal, 1994; Sevinga et al., 2004; Sairanen et al., 2009) and the rate of
inbreeding over time (ΔF) (Ehiobu et al., 1989; Sevinga et al., 2004; Pedersen et al.,
2005; Boer, 2007). The inbreeding coefficient F is classically defined as the
probability of an individual having two genes identical by descent (Wright, 1922). It
depends on the quality of the pedigree information and on pedigree completeness
and depth (Cothran et al., 1984; Boichard et al., 1997; Curik et al., 2003). Missing
pedigree information, even for the most recent generations of ancestors, could lead
to biases when estimating the rate of inbreeding (Boichard et al., 1997). Different
population sizes over time and an intensive use of preferred males could also cause
increasing changes in inbreeding coefficients (Nomura et al., 2001; Sierszchulski et
al., 2005). As investigated by Ehiobu et al. (1989) and Pedersen et al. (2005) faster
rates of inbreeding (ΔF) were found to have greater impact on the extent of
inbreeding depression than slower ones.
The two most common ways to estimate pedigree-based inbreeding coefficients for
large populations are the methods of Meuwissen and Luo (1992) and Van Raden
(1992). The alternative concepts of Ballou (1997) as well as new and ancestral
inbreeding coefficients by Kalinowski et al., (2000) were developed to ascertain when
inbreeding mostly evolves in a population. The inbreeding concept of Kalinowski et
al. (2000) splits the conventional inbreeding coefficient into two parts.
One part covers ancestral inbreeding, whereas the other one embraces new
inbreeding. Ancestral inbreeding involves all homozygous alleles which have met in
9
the past. On the other hand, new inbreeding allocates all alleles which are
homozygous for the first time (Mc Parland et al., 2009).
Another measure to derive the exposure of a population to inbreeding depression is
the effective population size (Ne) (Teegen et al., 2009). It is defined as the number of
individuals in an ideal population that would give rise to the same variance of gene
frequencies or the same rate of inbreeding as observed in the breeding population
studied (Falconer and Mackay, 1996). If pedigree data is available, effective
population size could be estimated from the increase in inbreeding over time (ΔF) as
suggested by (Wright, 1931):
revealed
. Studies by Meuwissen and Woolliams (1994)
fundamental relationships between the effective population size,
inbreeding depression and the genetic variances of fitness traits, respectively. They
concluded that the critical size for Ne, i.e. the size below which the fitness of the
population steadily decreases, lies between 50 and 100 animals. In closed
populations (e.g. the Trakehner or Holstein horse breeds), the effective population
size depends on the number of animals selected to be parents in each year, the
variance of the family size and the average generation interval (Meuwissen and
Woolliams, 1994).
Gómez et al. (2009) included the individual increase in inbreeding over time (ΔFi) as
a measure of inbreeding load into one of their models as a linear covariate to quantify
inbreeding depression for body measurements in Spanish Arab horses. ΔFi was
computed as ΔFi =
, where t is the number of generations. It was
suggested by González-Recio et al. (2007) and Gutiérrez et al. (2008) as an
alternative measure of inbreeding adjusted for the pedigree depth of an individual,
making it possible to distinguish between two animals with the same inbreeding
coefficient but differences in the number of generations in which this level of
10
inbreeding has appeared (Gómez et al., 2009).
The ΔFi coefficients share the
properties of ΔF (Falconer and Mackay, 1996) and, contrary to the Fi values, the
individual increase in inbreeding coefficients are expected to have a linear behaviour
over generations (Gómez et al., 2009). In the same work, Gómez et al. (2009)
applied the parameter δ (also described by Fox et al., 2007 and Charlesworth and
Willis, 2009) as δ =
, where
and
are the phenotypic values for each analysed trait for F = 0, F = 0.25 and for ΔFi = 0
and ΔFi = 0.25, respectively (Gómez et al., 2009). They defined the parameter δ as
the proportional decrease in the trait values in inbred individuals compared to
outbreds, which is expected to be 0 when there is no inbreeding depression.
Negative or positive values indicate that inbred individuals have lower or higher
performance than outbreds (Gómez et al., 2009).
Impact of inbreeding on studied traits
The majority of research projects dealing with the effect of inbreeding in various
horse breeds have focused on reduced female reproductive performance and the
occurrence of fertility disorders such as twinning, stillbirth, early abortion or retained
placenta (Mahon and Cunningham, 1982; Cothran et al., 1984; Klemetsdal and
Johnson, 1989; Langlois and Blouin, 2004; Sevinga et al., 2004; Wolc et al., 2006;
Van Eldik P. et al., 2006; Sairanen et al., 2009; Wolc et al., 2009) (Table 1). Female
fertility has mostly been evaluated using binary traits such as foaling rate (analysed
as the individual outcome of a mating) with a value of 0 if no foal was born and value
of 1 if a foal was born (Langlois and Blouin, 2004; Sairanen et al., 2009; Wolc et al.,
2009) or the conception rate, assessed as the conception rate per cycle and per year
(Cothran et al., 1984).
11
Table 1 Studies investigating the impact of inbreeding on various traits in different horse breeds
Study/Scope
Breed
n
Trait
Average inbreeding coefficient F(%)
Female reproduction and fertility disorders
Klemetsdal and Johnson (1989)
Norwegian Trotter
41,816
foaling rate
3.90, 4.30, 5.70 d)
Mahon and Cunningham (1982)
Thoroughbred
6,550
1.00
Cothran et al. (1984)
Standardbred horse
318
lifetime reproductive
performance a)
conception rate, foaling rate
10.3 (trotters), 7.40 (pacers)
1.01
1.02
15.6 – 15.7 c) (mean ΔF= 1.90)
Langlois and Blouin (2004)
b)
535,746
Sevinga et al. (2004)
French Warmblood,
French Coldblood
Frisian horse
52,392
numeric productivity
(declared foalings)
retained Placenta
Wolc et al. (2006)
Thoroughbred
2,033
twinning
n.s.
Sairanen et al. (2009)
Wolc et al., (2009)
Finnhorse,
Standardbred Trotter
Warmblood
32,731
33,679
3,965
foaling rate
foaling rate
foaling rate
3.60
9.90
n.s.
Male reproduction
Van Eldik et al. (2006)
Shetland pony
285
sperm quantity and quality
3.00
Boer, (2007)
Frisian horse
1,146
sperm quantity and quality
15.2
Gandini et al. (1992)
Italian Haflinger
4,736
morphological traits
1.21 (1925-33) – 6.59 (1979-87)
Dolvik and Klemetsdal (1994)
Norwegian Trotter
508
arthritis in carpal joints
3.90, 4.30, 5.70 d)
Curik et al. (2003)
Lipizzan horse
360
10.3
Sierszchulski et al. (2005)
Arabian
706
0.88
Gómez et al. (2009)
Andalusian horse
16,472
8.20 (mean ΔF= 1.00)
Norwegian Trotter
7,866
racing performance
5.50
Morphology and conformation
Performance
Klemetsdal, (1998)
a)
b)
c)
d)
Proportion of mare’s successful years at stud, adjusted for the decline in fertility with age, scaled to have an average of 1.0, and transformed to stabilise variance
Declarations of mating
Mean inbreeding coefficients of the foals born in 1999 and 2000, respectively
Mean level of inbreeding for the potential offspring, mares and stallions, respectively
12
The findings for the impact of inbreeding on female fertility in different horse breeds
are inconsistent. Most of the studies investigating genetic effects on foaling or
conception rates have not been able to clearly emphasise the negative genetic
impact on female reproductive efficiency (Mahon and Cunningham, 1982; Langlois
and Blouin, 2004; Wolc et al., 2006; Wolc et al., 2009).
In the study by Mahon and Cunningham (1982) on inbreeding and the inheritance of
fertility in the thoroughbred mare, the lifetime reproductive history of a mare was used
to calculate the average adjusted number of live foals per year at stud and was
summarised in a fertility score. The measure was computed as the proportion of
successes for each mare, but with the outcome of each year at stud weighted by the
reciprocal of the proportion of successes for mares of that age in the population of
mares. The inbreeding coefficient was treated as an independent covariate on which
the fertility score was regressed. As a result, recent inbreeding was not seen as an
important source of variation in fertility since the mating of close relatives was rare.
Although lower fertility was associated with inbreeding, the effect was not statistically
significant. Discussing their results, the authors stated that selection, both natural and
artificial, counteracted any effect of inbreeding on fertility (Mahon and Cunningham,
1982).
Cothran et al. (1984) detected a statistically significant trend for conception and
foaling rate to decrease with increased inbreeding. However, this relationship
accounted for less than two percent of the variation. In addition, the relationship
between reproductive performance and inbreeding was not consistent between the
Standardbred populations of pacers and trotters. Pacers showed the usual negative
relationship between inbreeding and reproductive performance. The trend for the
trotters indicated an increased reproductive potential with greater inbreeding
(Cothran et al., 1984).
13
Similarly to Mahon and Cunningham (1982), they also discussed that, in the
presence of selection, the magnitude of inbreeding depression is dependent on the
rate of inbreeding as well as on the overall inbreeding level. They generally
concluded that inbreeding does not appear to be a significant factor influencing
reproductive performance in Standardbred horses (Cothran et al., 1984).
Sairanen et al. (2009) investigated the effects of inbreeding and other genetic
components on equine fertility for Standardbred trotters (SB) and Finnhorses (FH).
The average level of inbreeding was 9.9% in the SB and 3.6% in the FH population.
Average foaling rates were better in the SB (72.6%) than in the FH (66.3%), but
intense inbreeding had a statistically significant negative effect on foaling rate within
each breed (Sairanen et al., 2009). Instead of using inbreeding coefficients as linear
covariates, as had been done in earlier studies on horses, their attempt was to study
the effects of different levels of inbreeding within a breed. Corresponding to results in
cattle and as previously discussed by Mahon and Cunningham (1982) and Cothran
et al. (1984), Sairanen et al. (2009) were also able to show that the effect on fertility
became more distinct after reaching a certain level of inbreeding. It was stated that
the avoidance of matings with very high inbreeding coefficients would improve foaling
rates (Sairanen et al., 2009).
A nearly significant effect of inbreeding on foaling rate (p = 0.08) was found in
Norwegian trotters by Klemetsdal and Johnson (1989). The foaling rate declined by
0.43% per 1% increase in the inbreeding coefficient of potential offspring.
Additionally, a total of 32 out of 354 mares showed early abortion. The occurrence of
early abortion was significantly affected by the inbreeding coefficient and the age of
the mare (Klemetsdal and Johnson, 1989). A one percent increase in the mares
inbreeding coefficient increased the frequency of early abortion by 1.27%
(Klemetsdal and Johnson, 1989).
14
Besides the potential of moderate selection for fertility in mares to compensate or
counteract for inbreeding depression (see also: Mahon and Cunningham, 1982), they
discussed the accuracy of fertility measurement. They hypothesised that if fertility is
recorded precisely, horses would show inbreeding depression, as would most other
livestock species (Klemetsdal and Johnson, 1989). The problem of accuracy and
consistency in data recording was also addressed by Mucha et al. (2012)
investigating fertility and twinning in Thoroughbred horses. It was suggested that data
quality is one of the most important problems in the analysis of fertility and fertility
disorders in horses.
Motivated by the hypothesis that the incidence of retained placenta (RP) in Friesian
horses is associated with inbreeding, the objectives of Sevinga et al. (2004) were to
calculate the inbreeding rate in the total registered Friesian horse population and to
study the association between the inbreeding coefficients of foal and mare and the
incidence of retained placenta. Additionally, heritability of RP in Frisian mares after
normal foaling was studied. Inbreeding rate (ΔF) of the total base population
(1979 to 2000) was estimated at 1.9%. The effective population size (Ne) was
estimated at 27 individuals. The regression coefficients for the incidence of RP on
inbreeding coefficients of the foal and the mare were found to be 0.12 ± 0.052 and
-0.016 ± 0.019 respectively. Mean heritability estimates of RP as a foal trait and as a
mare trait were 0.046 ± 0.088 and 0.105 ± 0.123, respectively. It was concluded that
in order to avoid further increase in the incidence of RP in Frisian mares, a decrease
in the inbreeding rate is required by increasing the effective breeding population. The
findings indicate that the high incidence of RP in Frisian horses is at least partly a
result of inbreeding (Sevinga et al., 2004).
A small number of research papers have discussed the context of reduced stallion
fertility and inbreeding (Van Eldik et al., 2006;Boer, 2007). These research projects
15
have provide indications for the impacts of inbreeding (Van Eldik et al., 2006;Boer,
2007). A study of inbreeding effects on semen quality in 1,146 Frisian stallions was
carried out by Boer (2007). The degree of inbreeding and the ancestral
decomposition of inbreeding was calculated for each stallion analysed. 26 ancestors
were observed to investigate whether inbreeding on these specific ancestors can
influence semen quality. Mean inbreeding, estimated over the entire pedigree, was
found to be 15.2 ± 1.75 % and ejaculate volume increased at higher inbreeding
levels. Specific inbreeding in 12 out of 26 ancestors analysed had a significant effect
(either positively or negatively) on the total number of motile sperms, the ejaculate
volume, the sperm cell concentration, motility class, morphologically normal
sperms (%) and abnormal acrosomes (%) (Boer, 2007).
Van Eldik et al., (2006) focused on the effects of inbreeding on semen quality in
Shetland pony stallions. The authors examined 285 immature Shetland pony stallions
e.g. for percentage of motile and morphologically normal sperm. The coefficients of
inbreeding ranged from 0 to 25% (av. F = 3.0 ± 4.6%). As mentioned earlier in
studies on female fertility (e.g. Sairanen et al., 2009), a certain level of inbreeding
also affects many aspects of sperm production and quality. In particular, coefficients
of inbreeding above 2% were associated with lower percentages of motile (p ≤ 0.01)
and morphologically normal sperm (p ≤ 0.001) (Van Eldik et al., 2006). Their findings
support the hypothesis that inbreeding has a detrimental effect on semen quality in
Shetland pony stallions. Estimating high values of heritability for semen
characteristics such as progressive motility (0.46) and concentration (0.24), the
authors summarised that these traits could be improved by phenotypic selection (Van
Eldik et al., 2006).
The effect of inbreeding on body conformation traits was investigated by Gandini et
al. (1992), Curik et al. (2003), Sierszchulski et al. (2005) and Gómez et al. (2009).
16
Gandini et al. (1992) analysed inbreeding and co-ancestry effects on body
conformation traits in Italian Haflinger horses. They stated a significantly decreasing
height at withers and girth of respectively 1.1 and 2.9 cm with a 10% increase in
inbreeding coefficient.
Sierszchulski et al. (2005) estimated the effect of inbreeding on height at withers,
chest circumference and circumference of the cannon as biometrical measures in
Arab mares (n = 706). Inbreeding coefficients were obtained from the additive genetic
relationship matrix. The effects of inbreeding rate were described using regression
coefficients in a linear animal model. The mean inbreeding level of mares was 0.88%
and no considerable effect of inbreeding was found. The obtained regression
coefficients were close to zero (Sierszchulski et al., 2005).
Investigating conformation traits for a much broader sample (n = 16,427), Gómez et
al. (2009) assessed inbreeding depression for body measurements in Spanish
Purebred (Andalusian) horses. The following eight measurements were recorded:
height at withers and chest, leg and body length, width of chest, heart girth
circumference, knee perimeter and cannon bone circumference. The biometric
values were directly obtained from the left side of the individual, using a Lydthin stick
and tape measure. To estimate genetic parameters and regression coefficients for
the individual inbreeding coefficient (Fi) and the individual rate of inbreeding (ΔFi),
multivariate animal models were used. The average Fi value for the whole population
was 8.2%. The average individual increase in inbreeding (ΔFi) was similar in males
and females for the total population and the animals measured (1% and 0.9%,
respectively) (Gómez et al., 2009). Their findings show significant inbreeding effects
on body measurements in Spanish Purebred (Andalusian) horses.
All of the regression coefficients estimated were negative and significant. Those for Fi
were around 10 times higher than those for ΔFi. The parameter δ was also negative
17
and significant (p ≤ 0.05), characterising inbreeding depression. They discussed that
inbreeding depression clearly appeared even though inbreeding levels and the
individual increase in inbreeding coefficients tended to decrease and to remain stable
for the breed studied in the last few decades of the 20th century (Gómez et al., 2009).
The ranking order of the individuals according to their EBVs was affected by the
inclusion of inbreeding measures into the evaluation models. They stated that the
likelihood of the models fitted including inbreeding measured to estimate genetic
parameters for body measurements is significantly higher than that of the simpler
model (Gómez et al., 2009). It was concluded that the inclusion of inbreeding
measures into the models to estimate variance components and EBVs for body
measurements could be advantageous in terms of more precise estimations (Gómez
et al., 2009).
In addition to pedigree information, Curik et al. (2003) applied molecular markers
from 17 dinucleotide repeat microsatellite loci dispersed over 14 different
chromosomes to analyse the impact of inbreeding on morphological traits in Lipizzan
horses (n = 360). Additionally, they examined association between individual
heterozygosity as well as mean squared distance (mean
) between microsatellite
alleles and morphological traits (Curik et al., 2003). Individual heterozygosity was
calculated as the number of loci at which a mare was heterozygous, divided by the
total number of loci at which a mare was scored (Curik et al., 2003). All mares were
measured for 27 morphological traits. Multivariate analysis of variance (MANOVA)
was used to assess the effects of inbreeding, heterozygosity and mean
on the
recorded conformation measures (Curik et al., 2003).
Significant associations were obtained between the length of the pastern-hind limbs
and the inbreeding coefficient (p ≤ 0.01), the length of the cannons-hind limb and
mean
(p ≤ 0.01) and the length of the neck and mean
18
(p ≤ 0.001). Thus, no
overall large effects of inbreeding, microsatellite heterozygosity and mean
on
morphological traits were observed in the Lipizzan horse (Curik et al., 2003).
Dolvik and Klemetsdal (1994) diagnosed arthritis in the carpal joints (carpitis) of
508 four-year-old Norwegian trotters and estimated their heritabilities. Individual
inbreeding coefficients were those calculated by Klemetsdal and Johnson, (1989).
Initially, the effect of inbreeding on bilateral and overall carpitis was inspected by
calculating the prevalence for groups of animals with similar inbreeding coefficients.
They performed a simultaneous estimation of the effect of inbreeding and sire. A
prevalence of 10 and 27% was reported for bilateral and overall carpitis, respectively.
Heritability estimates, based on data of 407 horses sired by 34 stallions, were 0.67
and 0.25. Significant effects of inbreeding on bilateral carpitis were estimated. The
probability of diseases was respectively, 6.7% and 12.3% among horses with lower
or higher inbreeding coefficient than average (Dolvik and Klemetsdal, 1994).
Further evidence for the presence of inbreeding depression of traits not directly
related to fitness is the study done by Klemetsdal (1998). He estimated the effect of
inbreeding on racing performance in Norwegian cold-blooded trotters, as measured
by accumulated, transformed and standardised earnings (ATSE). The estimated
regression coefficients were negative showing that the trait studied was depressed by
inbreeding. Klemetsdal (1998) also stated, focusing on racing performance, that
inbreeding depression depends on the overall level of inbreeding.
Conclusion
Although negative impacts of increased inbreeding in various livestock species are
known, the findings in horses are inconsistent. The negative effects of an increased
inbreeding coefficient (F) or of the rate of inbreeding (ΔF) could not been clearly
19
detected in the reviewed studies, independent of the trait studied. Some of the
authors refer to the fact that the magnitude of inbreeding depression is dependent on
the rate of inbreeding as well as on the overall inbreeding level. Additionally, it was
stated that the amount of F is dependent on the quality and depth of the pedigree
and that selection, both natural and artificial, has the potential to compensate for or to
counteract inbreeding depression. Incomplete and Inconsistent recording of
phenotypes was mentioned as one of the most important sources of error in the
detection of inbreeding depression, not only in fitness-related fertility traits.
Depending on the structure and depth of the pedigree as well as on sample size and
the quality of the phenotypes, fluctuations were observed in the extent of inbreeding
and its impact on the traits analysed when comparing the different studies. Nongenetic and environmental effects such as the age of the animal were confirmed as
the main factors influencing the traits investigated. Also in horses, the avoidance of
matings of closely related individuals could generally prevent the long-term negative
effects of inbreeding on reproductive performance as well as on pathological findings
and morphological traits.
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26
CHAPTER TWO
Investigations into genetic variability in Holstein
Horse breed using pedigree data
L. Roos1, D. Hinrichs1, T. Nissen2 and J. Krieter1
1
2
Verband der Züchter des Holsteiner Pferdes e.V., Abteilung Zucht, Kiel, Germany
Accepted for publication in Livestock Science
27
Abstract
A pedigree data set including 129,923 Holstein Warmblood horses was analyzed to
determine genetic variability, coefficients of inbreeding, the age of inbreeding and the
genetic contributions of founder animals and foreign breeds. The reference
population contained all horses which had been born between 1990 and 2010. The
average Pedigree Completeness Index (PEC) for the reference population was
determined as 0.88 and the average complete generation equivalent (GE) was
computed at 5.62. The mean coefficient of inbreeding for the reference population
(inbred and non-inbred horses) was 2.27%. Most of the inbreeding was defined as
“new” inbreeding, which had evolved during recent generations. The effective
population size and the effective number of founders were calculated to be 55.31 and
50.2 effective individuals respectively. The most influential foreign breed was the
English Thoroughbred with a contribution of 25.98%, followed by Anglo Normans
(16.38%) and Anglo Arabians (3.27%). At 2.75%, Hanoverian Warmblood horses
were determined to be the most important German horse breed. The stallions Cor de
la bryere, Ladykiller xx and Cottage son xx were found to be the most important male
ancestors. The mare Warthburg was defined as the most affecting female. It was
possible to detect the occurrence of the loss of genetic diversity within the Holstein
horse breed, related to unequal founder contributions caused by the intensive use of
particular sire lines. However, a slight increase in the effective population size and a
stagnation of inbreeding during the last generation might show the impact of more
open access given to foreign stallions in the recent past.
Keywords: effective population size, foreign breeds, genetic diversity, horse,
inbreeding
28
Introduction
Based on its success in international riding competitions, the Holstein horse breed
has become one of the most popular breeds, especially in show jumping.
The official breeding association was founded in 1935 and today’s complete breeding
population includes 7,693 registered mares and 225 licensed stallions within twelve
breeding districts. In the 19th century, the Holstein horse breed was influenced by the
Yorkshire Coach horse and by Thoroughbreds (Löwe, 1988).
Due to rising mechanization, the breeding goal has shifted from medium- weight draft
or riding horse for agricultural and cavalry use (before 1950) to a large framed,
athletic and expressive sport horse with a preferential aptitude for show jumping.
This process of refinement has been driven by an increased use of English
Thoroughbred and Anglo- Norman stallions.
Together with the Trakehner Horse breed, the Holstein horse is the unique German
sport horse breed working with closed studbooks.
Accordingly, the studbook for mares is strictly closed and the use of stallions from
foreign breeds in terms of breeding trails is minimized. Due to the increased use of
artificial insemination and against the background of the intensive use of certain
sires, an increase in terms of the rate of inbreeding and the contributions of fewer
ancestors is probable. A refreshment of previous knowledge is needed concerning
the composition of the Holstein gene pool.
There has not been any investigation concerning genetic composition of Holstein
horse breed. However, Hamann and Distl (2008) and Teegen et al. (2009) did some
research on the population structure of the Hanoverian and Trakehner breed
respectively.
29
Therefore, the aim of this study was to point out the updated levels of inbreeding, the
proportion of foreign blood and to specify the genetic contributions of outstanding
founders to the current structure of breeding stock. Additionally, the study applied
some alternative concepts regarding the evolvement of inbreeding.
Material and methods
Pedigree data
Pedigree data used for this study was provided by the Association of Holstein Horse
Breeders (Kiel/Germany) with support of the “Landeskontrollverband SchleswigHolstein” which is assigned to administer the pedigree data base. In 2010 the whole
pedigree data set contained 131,272 animals.
After revision and verification, a data-set of 129,923 animals with 55,796 males and
74,127 females was included in the analysis. Approximately 1% of undetermined
data was excluded.
The reference population applied in this study included all horses born between 1990
and 2010 (n = 78,677, with known parents). The first recorded ancestor was born in
the year 1869. Choosing a reference population consisting of all animals born in a
period of two generation intervals, the intension was to depict inbreeding situation for
the actual breeding stock completely as possible. Even if some of the animals died or
probably not used anymore, evaluating a shorter period of time would exclude
reproductive individuals and their progeny from the analysis (e.g. competing mares,
resuming their breeding use after several years).
30
Data analysis
The following parameters of population structure were exploited in the analysis for all
horses within the reference population, based on the whole pedigree data-set: The
average coefficient of inbreeding, the effective number of founders, the effective
number of ancestors and the effective number of founder genomes. Additionally, the
generation intervals were determined for the four pathways sire to sire, sire to dam,
dam to sire and dam to dam. Therefore, the average age of the parents at the time of
birth of their first reproductive offspring was used.
To identify the amount of pedigree completeness and to quantify the possibility to
ascertain inbreeding, the pedigree completeness index (PEC) (Mac Cluer et al.,
1983) was computed as follows:
=
,
where Csire and Cdam are the amount of pedigree information contributed by the two
parental lines.
To specify the number of entire generations, the complete generation equivalents
(GE) were calculated thus for each individual j:
=∑
/2 ,
where ni is the number of known ancestors in generation i and g is the number of
known generations for individual j.
In case of individuals with two unknown parents, animals were considered as
nonrelated founders. The contribution of founders could have been different, because
some of them had been used with a greater intensity than others.
31
Due to this fact, the amount of founders provided less information about the genetic
diversity of a population.
To overcome this problem, Lacy (1989) introduced the effective number of founders
(fe), defined as the number of equally contributing founders expected to produce the
same genetic diversity as the population under study. The more equal the
contributions of the founders the greater is the effective number of founders.
In case of an equal contribution of all founders, the effective and actual number of
founders is the same.
Boichard et al. (1997) developed another characteristic factor to clarify genetic
diversity with regard to the loss of allelic diversity. The so called effective number of
ancestors (fa) also embraced for the contributions of all ancestors and was defined as
the minimum number of ancestors explaining the complete genetic diversity of the
current population. The computation of this parameter was predicated on the
marginal contributions of the 1,000 most important ancestors.
Bottlenecks or a frequent use of special sires and their offspring are known as
reasons for the loss of allelic variability. To identify ancestors which influenced the
genetic composition of the population more than others, it was necessary to look at
the difference between the number of effective founders and effective ancestors.
A larger amount of effective founders in proportion to the number of effective
ancestors referred to ancestors which assisted the formation of the population to a
greater extent than others (Boichard et al., 1997). The underlying fact was that the
contributions of ancestors did not matter for the generations when they are
marginalized.
The effective number of founder genomes (fg) was defined by Lacy (1989) as “that
number of equally contributing founders with no random loss of founder alleles in
descendants that would be expected to produce the same genetic diversity as in the
32
population under study”. The Gene drop procedure introduced by Boichard et al.
(1997) was used to compute the number of effective founder genomes. Because the
use of breeding animals is not equal in each generation, alleles can be lost during the
formation of a population.
Considering this, the effective number of founder genomes is sensitive to the depth of
the pedigree and is smaller than half of the effective population size, the effective
number of ancestors and the effective number of founders (Hamann and Distl, 2008).
Inbreeding coefficients: The inbreeding coefficient (F) was defined as the probability
of an individual having two genes identical by decent (Wright, 1922). F-values were
calculated by the two methods of Meuwissen and Lou (1992) and Van Raden (1992).
The alternative concepts of Ballou (1997) as well as new and ancestral inbreeding
coefficient by Kalinowski (2000) were applied to ascertain when inbreeding mostly
evolves in the population. Ballou`s ancestral inbreeding coefficient (Fa) was
computed as:
=
( )
+ !1 −
( )$ ( )
+
(%)
+ (1 −
(%) ) % &/2
where Fa is the ancestral inbreeding coefficient for an individual, F is the inbreeding
coefficient and the subscripts s and d represent the inbreeding values for the sire and
the dam of that individual.
Ancestral inbreeding devised by Ballou (1997) is the cumulative amount of an
individual`s alleles which have been previously exposed to inbreeding in its
ancestors. Inbreeding arising from every common ancestor out of the individual’s
pedigree is contained in Ballou`s concept of ancestral inbreeding.
33
The inbreeding concept of Kalinowski et al. (2000) split the conventional inbreeding
coefficient into two parts. One part covered ancestral inbreeding, whereas the other
one embraced new inbreeding.
As described by McParland et al. (2009), ancestral inbreeding involves all
homozygous alleles which have met in the past. On the other hand, new inbreeding
allocates all alleles which are homozygous for the first time.
It should be mentioned, that Kalinowski`s ancestral inbreeding coefficient only
includes ancestral inbreeding of relationships.
This means that the common ancestor could be found on both sides of the pedigree,
in the sire line as well as in the dam line. Thus, if the classical inbreeding coefficient
is 0, ancestral inbreeding is also 0 (McParland et al. 2009).
Effective population size: The expected effective population size (Ne) was estimated
with the help of the classical approach described by Sölkner et al. (1998), based on
the increased inbreeding coefficient (∆F) between the last generation of the
reference population and the parents of those individuals [Ne = 1/(2∆F)].
Increased inbreeding coefficients (∆F) were computed with:
∆F = −
1−
(
()*
()*
where Ft and Ft-1 are the average inbreeding at t and t – 1 generations.
Additionally, foreign breed genetic contributions were calculated for English
Thoroughbred, Hanoverian Warmblood, Anglo Normans (Selle Francais) and Arabian
blood lines.
34
The software package PEDIG (Boichard, 2002) was used to calculate pedigree
completeness index, complete generation equivalent, generation interval, inbreeding
coefficients, the effective number of founders, the effective number of ancestors, the
effective number of founder genomes and the marginal contributions of ancestors.
Results
Data quality and Generation Interval
The Pedigree completeness index (PEC) and the complete generation equivalents
(GE) were computed to describe the quality of the Pedigree data. The average PEC
over five generations for the reference population was determined as 0.88 and varied
between 0.78 in 1990 and 0.95 in the year 2010.
For the total reference population, the average GE was 5.62 with an increasing
tendency of 4.78 in the year 1990 and 6.53 in 2010 (Table 1). The average
generation interval for the 4 pathways of the reference population was computed as
10.3 years, with a variation between the pathways from 10.03 to 10.59 years.
35
Table 1 Metrics of pedigree analysis for the Holstein Warmblood reference
population
Item
Value
Total population, n
129,923
Inbred individuals, n
94,544
Reference population (known parents), n
78,677
Average Pedigree completeness index (PEC)
0.88
Average Complete generation equivalent (GE)
5.62
Average generation interval, years
10.31
Effective population size, n
55.31
Founders, n
3,194
Average inbreeding coefficient total population (all horses), %
1.57
Average inbreeding coefficient total population (inbred horses), %
2.17
Average inbreeding coefficient reference population (all horses), %
2.27
Average inbreeding coefficient reference population (inbred horses), %
2.47
Effective founders, n
50.20
Effective ancestors, n
28.55
Effective founder genomes, n
16.78
Ancestors to explain 50% of gene pool, n
11
52
78
229
Gene pool explained by 1,000 ancestors, %
95.14
Inbreeding
The average inbreeding coefficient for the reference population (all horses) was
estimated as 2.27% (Table 1). Including only the inbred individuals, the value raised
to 2.47%. For the whole population, a value of 1.57 % was computed (Table 1).
The inbreeding coefficient over all horses included in the reference population (inbred
and non-inbred individuals) has nearly tripled in 2010 (2.9 %) compared to 1990
(1.1%) (Figure 1).
36
Figure 1 Development of average inbreeding (F%) per birth year for the reference
population (inbred and non--inbred horses)
With regard to the different types of inbreeding coefficients against the background of
the evolvement of inbreeding, it becomes clear that most of the inbreeding occurred
in recent generations. With a mean value of 1.38 %, Kalinowski`s new inbreeding
coefficient is obviously higher than the ancestral inbreeding coefficient with 0.08%
respectively (Table 2). This means that over 90% of the classical inbreeding (F =
1.47%) evolved in the five most recent generations. Only a small proportion of
Wright`s inbreeding coefficient could be defined as “old” inbreeding, which evolved
more than five generations ago,
ago possibly influenced
d by
comparatively limited
pedigree knowledge at that time. The ancestral inbreeding coefficient developed by
Ballou (1997) was computed at 2.14 %.
Table 2 Metrics (%) of different inbreeding coefficients
µ
ơ
Max
Classical inbreeding (F) (Wright, 1922)
1.47
2.01
31.36
New inbreeding (Kalinowski, 2000)
1.38
1.89
27.95
Ancestral inbreeding (Kalinowski, 2000)
0.08
0.17
4.68
Ballou`s inbreeding (Fa) (Ballou, 1997)
2.14
2.23
16.66
Inbreeding coefficient
37
Effective population size and genetic contributions
c
The effective population size was calculated as the average effective population size
of the two generations included in the reference population. The estimated Ne was
55.31 (Table 1).
In terms on the development of the effective population size, Figure 1 illustrates an
obvious trend for a decreasing number of effective
effective animals from 1950 to the year
2000. The most conspicuous decline is shown between 1960 and 1980 (Figure 2).
A slight increase of Ne from 49.45 (until 2000) to 61.18 animals (until
(until 2010) becomes
apparent (Figure 2) during the last generation considered (2000 – 2010).
Figure 2 Development of effective population size (Ne) per generation
The effective number of founders was estimated at 50.2 and the effective number of
ancestors at 28.55. The ratio between these two values is 1.75 (Table 1). Half of the
gene pool of the reference population is defined by 11 animals. 90% of the gene pool
is explained by 229 individuals. The first 1,000 most influential ancestors make up
95.14%
5.14% of the genetic pool (Table 1).
Due to breeding policies, the gene pool of the reference population is mainly
determined by Holstein blood lines. Holstein Warmblood
Warmblood horses made up 40.12 % of
the reference population under study.
38
At 25.98 %, the English
sh Thoroughbred was acknowledged as the most influential
foreign breed (Figure 3). As well as Thoroughbred horses, French or Anglo Norman
blood lines were used to leverage the process of refinement.
The contribution of these breeds (Selle Francais) was estimated
timated with 16.38%. The
most influential German
erman breed was the Hanoverian Warmblood
W armblood horse with a
proportion of 2.75%. Other German breeds contributed a very low percentage (<
1%). Arabian or Anglo Arabian blood lines affected 3.27 % of the genetic
conformation (Figure 3).
Figure 3 Genetic contributions of foreign
foreign breeds (%) to the Holstein Warmblood
W
reference population
The influential character of some foreign breeds on the reference population became
significant again with regard to the most formative animals.
The five most fundamental stallions are represented by one Anglo Norman, one
Holstein, two English Thoroughbreds
Thoroughbreds and one Anglo Arabian Stallion (Table 3). With
a marginal contribution of 11.55% the French stallion Cor de la bryere was the most
impressive ancestor by far (Table 3).
39
Table 3 Genetic contributions (%) of the 15 most influential stallions in the Holstein
Warmblood reference population
Year
of birth
Total
contribution
Marginal
contribution
Cor de la bryere AN
1968
11.50
11.55
Ladykiller xx
1961
8.61
8.61
Capitol I
1975
6.81
6.81
Cottage son xx
1944
5.40
4.55
Ramzes AA
1937
4.74
3.07
Loretto
1932
3.83
3.05
Marlon xx
1958
2.04
2.04
Alme AN
1966
2.03
2.03
Farnese
1960
2.32
1.74
Ramiro
1965
3.36
1.47
Heidelberg
1941
1.94
1.19
Anblick xx
1938
2.08
1.16
Manometer xx
1953
1.78
0.98
Quidam de Revel SF
1982
1.20
0.90
Makler I
1929
1.49
0.90
Stallion
The two English Thoroughbred stallions Ladykiller xx and Cottage son xx affected the
reference population with 8.61% and 4.55% respectively.
The sire Capitol I was found to be the most influential Holstein stallion. The Anglo
Arabian stallion Ramzes A.A. is also one of the most founding ancestors (Table 3).
The contribution of the stallion Cor de la bryere continued to expand as a
consequence of its high number of successfully competitive and breeding progeny
(e.g. Caletto I and II or Calypso I and II). His genetic impact increased from
approximately 10 % (1990 – 1993) up to 13 % in the years 2006 – 2010 (Figure 4).
40
Figure 4 Development of marginal genetic contributions (%) of the most
mo formative
sires in Holstein Warmblood
armblood reference population per birth year
The most increasing trend affecting today`s breeding animals could be determined
for Capitol I. His genetic impact was 2.5 % in the years 1990 - 1993 and 10.3% from
2006 until 2010 (Figure 4). A decreasing trend was found
fo
for the L- line (Ladykiller xx)
and the comparatively low represented A-line
A
(Alme) (Figure 4).
The breeding mares Warthburg (3.70%), Tabelle and Deka as mothers of
outstanding and strongly used stallions like Landgraf, Calypso I and Caletto I were
the
e most affecting female ancestors (Table 4).
41
Table 4 Genetic contributions (%) of the 10 fundamental breeding mares in the
Holstein Warmblood reference population
Mare
Year
of birth
Total
contribution
Marginal
contribution
Warthburg
1962
3.70
3.70
Tabelle
1959
2.77
2.43
Deka
1967
2.90
2.13
Dorette
1956
1.41
1.41
Ricarda
1957
1.15
1.01
Kuerette
1973
0.80
0.80
Heureka
1960
0.86
0.75
Furgund
1969
0.92
0.59
Isidor
1972
1.35
0.55
Usa
1960
0.54
0.47
Discussion
The PEC and the GE are appropriate tools to assess the quality of the pedigree data.
The PEC for Holstein horse breed over 5 generations was 0.88 and varied between
0.78 in 1990 and 0.95 in 2010. The average GE was 5.62 and ranged between 4.78
in 1990 and 6.53 in 2010.
Hamann and Distl (2008) calculated a higher average GE of 8.34 for the Hanoverian
reference population. A nearly similar GE of 5.70 was computed by Cervantes et al.
(2008) for Spanish Arab horses. A low average GE of 2.9 was shown by Teegen et
al. (2009) for the Trakehner horse breed.
Computing the average inbreeding coefficient with the method of Meuwissen and Lou
(1992) and with that of van Raden (1992) was found to be indiscriminative. The
increase in inbreeding per time was 1% in the first generation of the reference
population.
42
However, a decline in the rate of inbreeding was observed within the last generation.
From 2000 to 2010 the value increased less than in the generation before (0.8%
compared to 1%). There was no further increase in inbreeding from 2008 (Figure 1).
The average inbreeding coefficient stagnated at 2.9% until 2010. In comparison,
Hamann and Distl (2008) calculated an average inbreeding coefficient for a
Hanoverian Warmblood reference population (all horses born between 1980 and
2000) of 1.33%.
The variation of average inbreeding did not exceed 0.3% over all horses and in
mares (Hamann and Distl, 2008). In Hanoverian stallions, the average inbreeding
coefficient per birth year was found to lie between 0.9 and 1.59% (Hamann and Distl,
2008). One reason for the increase in average inbreeding per time in Holstein
Warmblood could be the concentration on only few stallions out of the previously
described stallion lines.
Investigations into the average inbreeding of other breeds determined 6.59% for
Italian Haflinger horse (Gandini et al.,1992), 7.0% for Spanish Arab horses
(Cervantes et al., 2008), 8.48% for Andalusian horses (Valera et al., 2005), 8.99 %
for North American Standardbreds (McCluer et al., 1983), 10.81% for Lipizzan horses
(Zechner et al., 2002), 12.5% for Thoroughbred horses (Mahon and Cunningham,
1982) and 15.7% for Friesian horses (Sevinga et al., 2004).
Analysing the period of time in which most of the inbreeding occurred in the Holstein
breed, it could be determined that over 90% of the classical inbreeding evolved
during the last five generations. It could be defined as “new” inbreeding with its origin
between the years 1960 and 2010.
Access of different breeds into the Holstein breeding program is limited compared to
the programs of other German horse breeds. Following the principles of pure
breeding, the studbook for the mares is completely closed. Therefore, a greater
43
inbreeding coefficient was expected compared with the Hanoverian Warmblood
breed.
The average effective populations size (Ne) for the Holstein Warmblood reference
population was estimated to be at a low level of 55.31. However, a slight increase in
Ne within the last generation (2000 – 2010) is obvious. The value rose from 49.45
effective animals in the penultimate generation (1990 – 2000) to 61.18.
This increase in effective population size is by definition linked to the previously
described decline in the rate of inbreeding occurrence (∆F) during the last
generation. The opened access of foreign breeding animals to the stallion stock in
the past may have accelerated this development. Sevinga et al. (2004) estimated an
effective population size of 27 animals for the Frisian horse. An effective population
size of 158 animals was calculated by Teegen et al. (2009) for the Trakehner horse
breed using the Numerator Relationship Matrix (NRM). For the Hanoverian
Warmblood, Hamann and Distl (2008) computed a value of 372.34 effective animals.
It is possible to make statements about the effective number of founders due to the
close relationship between the effective population size and other parameters
deviated from the probability of genetic origin. The effective number of founder
animals for the Holstein Warmblood reference population was computed as 50.2.
Mahon and Cunningham (1982) calculated a lower value of 28 effective founders for
the Thoroughbred. This value is comparable to the values of the Spanish Arab horse
calculated to be 39.5 (Cervates et al., 2008), for the Lipizzan horse 48.2 effective
founders
(Zechner et al., 2002) and the Carthusian strain of Andalusian horses
(Valera et al., 2005) with 39.6 effective founders, respectively. Much higher values
were estimated by Hamann and Distl (2008) calculated 244.9 effective founders for
the Hanoverian Warmblood horse.
44
The contributions of important ancestors to the Holstein horse gene pool is not as
balanced as described for other horse breeds. 50% of genetic variability of the gene
pool can be explained by 11 important animals. 229 animals made up 90% of the
genetic composition of the breed. Hamann and Distl (2008) determined 111 animals
to explain 50% and 930 ancestors to interpret 90% of the Hanoverian genetic
formation.
The unbalanced arrangement of important ancestors` contributions in Holstein horses
is a further characteristic of the strong use of particular sires and could be deemed as
a reason for the loss of genetic variability. Considering this fact, the need to achieve
the objectives of refinement could be defined as a historically based reason.
In the second half of the 20th century, there was comprehensive use of Thoroughbred
and Anglo Norman stallions in conjunction with an increased concentration on only a
few of this stallion lines.
The Holstein breeding area was one of the largest application regions for English
Thoroughbreds (Löwe, 1988). In 1972, the percentage of English Thoroughbred sires
in the Holstein stallion stock constituted 33% (Löwe, 1988).
Based on the offspring of these English Thoroughbred, Anglo Norman and Anglo
Arab sires, the stallion lines were established in mating with original Holstein mares
from the accurately managed mare lines. Some of these line-founding stallions, such
as Cor de la bryere, Ladykiller xx, Cottage son xx and Ramzes, still imprint the
current Holstein breeding population in a different proportion . At least, the two most
frequented stallion lines (Cor de la bryere - line and Ladykiller xx – line) accounted for
this unbalanced arrangement of blood lines with their strongly used male offspring.
It became obvious that some founders had been used more intensely than others
considering 50.2 effective founders compared with 3,194 founders within the
45
reference population. In the Hanoverian reference population the effective number of
founders was 244.9 compared with 13,881 founder animals (Haman and Distl, 2008).
They also concluded that particular sires were utilised more often than other ones. An
existing ratio between the effective number of founders (fe) and the effective number
of ancestors (fa) could be used as a further evidence for the random loss of genetic
diversity.
A ratio fe/ fa of 1.75 was detected for the Holstein reference population. This fact also
implies the intensive use of particular sire lines. Another indicator of the occurrence
of allelic loss from founder animals is the difference between the effective number of
founder genomes (fg = 16.78) and the effective number of ancestors (fa= 28.55). For
the Holstein horse breed, this ratio was estimated to be 1.70.
Conclusion
The results of this study illustrate the occurrence of the loss of genetic diversity within
the Holstein horse breed related to unequal founder contributions caused by the
intensive use of particular sires or sire lines. Linked to this fact, it should be
mentioned, that most of the inbreeding occurred in the newer generations. However,
with a closer look at the recent past, we were able to observe an increase in the
number of effective animals (Ne) in conjunction with a stagnating tendency in the rate
of inbreeding (∆F).
It might be caused by some changes in breeding policies, especially against the
background of foreign stallions` access to the breeding program. To follow this path
with caution could be one possibility to preserve a needed volume of genetic
variability in the Holstein horse breed. Further investigations must be carried out into
the consequences of inbreeding and allelic loss in Holstein horses, especially for
functional traits. Therefore, phenotypic data will be related to the results of the
46
present pedigree analysis to clarify the risks of inbreeding depression or the
presence and impact of purging, essentially for health and fertility.
Acknowledgements
This research project was kindly supported by the H. Wilhelm Schaumann
Foundation (Hamburg, Germany) and the Association of Holstein Horse Breeders
(Kiel, Germany).
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49
CHAPTER THREE
Effect of inbreeding on female fertility in Holstein
horse breed
L. Roos1, C. Heuer1, D. Hinrichs1, T. Nissen2 and J. Krieter1
1
2
Verband der Züchter des Holsteiner Pferdes e.V., Abteilung Zucht, Kiel, Germany
50
Abstract
Mating and foaling data (n = 379,458) of Holstein Warmblood mares were analysed
to study the possible impacts of inbreeding and other relevant factors (e.g. age effect)
on female fertility and to estimate heritability. Generalised linear mixed models were
used to estimate variance components for the following traits: the foaling rate
(individual outcome of a mating, foal or no foal), the occurrence of fertility disorders
(stillbirth) and the outcome of the season’s first mating (foal or no foal). The average
inbreeding coefficient for the whole Holstein horse population was estimated at
1.57%. For the subsets of mares and expected foals analysed the mean inbreeding
estimates were 1.58% and 0.93%, respectively. Increased inbreeding had a
significantly positive effect on the individual foaling rate (p ≤ 0.05) and the outcome of
the season’s first mating (p ≤ 0.05) when including the mares inbreeding coefficient
as a covariate. Significantly negative effects of inbreeding on the frequency of
stillbirth (p ≤ 0.001) were detected using the inbreeding coefficient of the expected
foal. All traits under investigation had estimates of heritability of less than 0.1. The
heritability of the individual foaling rate ranged between 0.024 and 0.033, depending
on the model used. If stillbirth was considered as a trait of the expected foal, the
estimate of heritability was estimated at 0.069. The value decreased to 0.008 when
stillbirth was treated as a trait of the mare. The findings have led to encouragement in
further research on the impact of inbreeding especially regarding fertility disorders.
Therefore, it is recommended to improve the recording of appropriate phenotypes in
future.
Keywords: horse, fertility, fertility disorders, stillbirth, foaling rate
51
Introduction
Fertility and the avoidance of fertility disorders are among the most important factors
in economic horse breeding. Breeding animals are expensive and the initial
investment to produce healthy offspring is comparatively high (Sairanen et al., 2009).
Equine fertility is also known as a tangled functional trait with lots of influential
environmental and management factors such as the age of the animal or the
individual servicing at farm level. Thus, it is difficult to determine the fundamental
factors directly linked to the individual (Mucha et al., 2012; Sairanen et al., 2009). Not
only in horses inbreeding is known as a genetic factor capable of affecting fertility,
depending on its severity (Charlesworth and Charlesworth, 1987; Charlesworth and
Willis, 2009; Falconer and Mackay, 1996). Previous studies by Cothran et al. (1984)
as well as Klemetsdal and Johnson (1989) showed tendencies that high inbreeding
may weaken fertility in horses. Holstein horse breed is known as a highly selected
population, particularly for their performance in sports and their jumping ability. The
studbook for the mares is strictly closed and access by foreign stallions is limited for
refinement and improved performance purposes. The population is mostly line bred
with concentration processes on certain sires from a few stallion lines. Against the
background of these conservative breeding policies, it is more common to have
closely related animals compared to more open or crossbred populations (Roos et
al., 2014, submitted)., The risk of negative effects on functional traits with low
heritability (e.g. health and fertility) increases with an increase in average inbreeding
accompanied by a decreasing effective population size. Due to this fact, the aim of
this study was to demonstrate the possible impacts of inbreeding and other relevant
factors (e.g. age effect) on fertility (foaling rate) and the occurrence of fertility
disorders (stillbirth) in Holstein warmblood horses.
52
Material and Methods
Dataset and observed traits
Pedigree and fertility data were provided by the Association of Holstein Horse
Breeders (Kiel, Germany). Covering and foaling records for 25,574 Holstein
Warmblood mares (birth years 1980 – 2009) for the seasons 1984 to 2011 were used
and 379,458 matings with 1,080 different stallions were analysed. Each mating was
treated as one record and consisted of the mare’s identification number (ID = unique
equine life number, UELN), the ID of the mare’s dam, the ID of the mare’s sire, date
of covering, age of the mare at mating, ID of the stallion used and the ID of the foal
produced in the case of a successful mating. However, the dataset does not cover
the whole breeding history of every broodmare, because the mating years were
restricted (1984 – 2011). To calculate the inbreeding coefficients of mares and
expected foals, the Holstein pedigree database (129,923 individuals) was used.
Structure, quality and depth of the pedigree were analysed in a previous study (Roos
et al., 2014, submitted).
The outcome of each mating, described as the individual level equivalent to the
foaling rate (see also: Sairanen et al., 2009) was treated as a binary trait with a value
of 1 if a live foal was born and value of 0 if no foal was born. A mating was declared
successful if the offspring received an individual registration number (UELN). A total
of 80,538 foals born alive were recorded in the observed period. The mean number
of progenies per sire and per mare was estimated at 75 and 3, ranging from 1 to
2,499 and 1 to 24 descendants, respectively. However, the reasons for a value of 0
concerning this trait were not entirely registered and no results of any pregnancy
examination were reported.
53
The second trait of the study was the occurrence of stillbirth with a value of 1 if
stillbirth was reported, and a value of 0 if no stillbirth was reported. It was analysed
using a data file consisting of all matings resulting in a live-born foal or a stillbirth
(n = 81,775). Additionally, the outcome of the season’s first mating per mare was
analysed, using a value of 1 if a foal was born after the first insemination per season
and a value of 0 if no foal was born as result of first mating. In this dataset, only the
first insemination of a mare per season was considered (n = 127,684).
Models and factors
In a first step, fixed effects were tested for significance and were added stepwise into
the model, using the MIXED procedure in the SAS software(SAS Institute Inc., 2008).
A comparison of the different models was carried out, using the fit statistics “Akaike’s
information criteria” (AIC; Akaike, 1974) and “Bayesian information criteria” (BIC;
Schwarz, 1978). The models with the smallest AIC and BIC values were chosen for
the analysis of fertility traits.
The age class of the mare’s age at mating, the age class of the mare’s age at first
mating in lifetime and the season (combined effect of year and month of mating) were
included into the analysis as fixed effects. The age of the mare at first mating and the
age of the mare at mating were grouped into four categories. Age class one
contained all mares at the age of five years and younger, class two consisted of all
mares at the age of six to ten years, class three included the mares at the age of
11 to 16 years and class four all mares older than 16 years of age. The inbreeding
coefficient of the covered mare was estimated using the software PEDIG (Boichard,
2002) as a part of a previous study (Roos et al., 2014, submitted). The inbreeding
coefficients for the expected offspring were estimates of the diagonal elements of a
54
numerator relationship matrix. Inbreeding coefficients were included into the given
models as covariates.
The program ASReml (Gilmour et al., 2008) was used to fit generalised linear mixed
models and to introduce random and genetic effects to estimate the heritability. The
mare = permanent environmental effect of the mare, the animal = additive genetic
effect of the mare (Model 1) or the expected foal (Model 2) and the
stallion = permanent environmental effect of the stallion were used as random
effects. As in Sairanen et al. (2009), both the mated mare (Model 1) and the
expected foal (Model 2) were used as a basic individual in separate models for each
trait. That is, the result was considered to belong to either the mare (produced a foal
or not), or to the foal (was born or was not born). Either the inbreeding coefficient of
the covered mare or that of the expected foal was used in the model depending on
the respective basic individual. The following mixed threshold model was assumed:
E
= Φ (inbrcoef + season + firstageclass + ageclass + mare
i
j
k
l
m
+animal + stalliono)
n
Where E
= the expected probability for the outcome of the mating (0/1), the
occurrence of stillbirth (0/1) and the outcome of first mating in season (0/1). Φ is the
cumulative probability function of the standard normal distribution. The fixed effects
are as follows: inbrcoefi = inbreeding coefficient of covered mare or expected foal
(linear covariable), seasonj = combined effect of month and year of mating,
firstageclassk = age class of mare’s age at first mating in lifetime and ageclassl = age
class of mare’s age at mating.
55
Results
Inbreeding
The average inbreeding coefficient for the whole Holstein horse population was
estimated at a moderate level of 1.57%. For the analysed subset of mares
(birth years 1980 – 2009) the mean value of inbreeding was estimated at 1.58% and
varied from 0 to a maximum of 27.1%. Fewer than 150 mares (0.57%) had an
inbreeding coefficient of 10% or higher. Most of the mares (57.9%) were inbred with a
value lower than 1.5%. The mean value of inbreeding for the expected foal was
estimated at 0.95% and ranged from 0 (MIN) to 25.0% (MAX). For more details, see
Roos et al. (2014, submitted).
Foaling rate
The average foaling rate (ratio of foaled mares/covered mares) for Holstein
Warmblood broodmares in the analysed period (1984 – 2011) was estimated as
63.4%. Over the years, it has ranged between 73.1% (1996) and 47.6% (2011) with a
decreasing trend since 2006. A significant positive effect of inbreeding on the
individual equivalent of the foaling rate (outcome of each individual mating, 0/1) was
observed (p ≤ 0.05) when the inbreeding coefficient of the mare was used in the
model (Model 1). The linear regression coefficient was estimated at 0.122 ± 0.282
(p = 0.021). A one per cent increase in the mares’ inbreeding coefficient increased
the probability of a live-born foal by 0.01%. A significant impact was also detected for
the age of the mare (age class) at mating (p ≤ 0.001, Table 1) and for the age of the
mare at first mating (p ≤ 0.001) as well as for the season (p ≤ 0.001). The individual
outcome of mating decreases equally with an increase in the mare’s age at mating
(Table 1) and with a rising age at first insemination, independent from the model
used. Mares at the age of five years and younger had the highest mating success
56
(individual mating outcome, 0/1) with an estimated value of 0.352 ± 0.014
(Model 1, Table 1). The worst individual mating outcome was estimated for age class
4 with an estimated value of 0.253 ± 0.011 (Table 1). The impact of the season
reflected the requirements of a mare regarding her reproductive physiology, whereby
horses are known as “long day” breeders (cycling when the days grow longer).Thus,
most of the matings (65.4 %) were done in April, May and June.
Table 1 LSQ-means (LSQ) and standard error (s.e.) by the age of the mare at mating
(age class) for the individual outcome of a mating in the two different models
Age class
n
Model 1*
Model 2**
LSQ
LSQ
s.e.
s.e.
1 (≤ five years of age)
116,930
0.352 ± 0.014
0.370 ± 0.013
2 (six to 10 years of age)
131,089
0.345 ± 0.014
0.361 ± 0.013
3 (10 to 16 years of age)
89,192
0.307 ± 0.013
0.320 ± 0.012
4 (> 16 years of age)
42,247
0.253 ± 0.011
0.260 ± 0.011
*Mare as studied individual in the model (animal effect of the mare)
**Expected foal as studied individual in the model (animal effect of the expected foal)
Stillbirth
The number of recorded stillbirths in the dataset was 1,237. The proportion of
stillbirths to all of the reported foalings (n = 81,775), was estimated at 1.51%. The
occurrence of stillbirth was not affected by the level of inbreeding when the
inbreeding coefficient of the mare was used in the statistical model (Model 1).
However, when stillbirth was treated as trait of the expected foal (Model 2), it was
affected significantly negatively by the inbreeding coefficient of the progeny. The
linear regression coefficient was estimated at 6.77 ± 2.33. A one per cent increase in
the foals’ inbreeding coefficient increased the risk of stillbirth by 0.67%. The age of
57
the mare at first insemination was not significant for the characteristic values of the
trait. In both of the used models, the season affected the number of stillbirths in a
significant way. The age of the mare at mating had a significantly negative effect on
the occurrence of stillbirth for both of the models used (p ≤ 0.001, Table 2). An
increasing trend in stillbirths with an increasing age of the mare was observed.
Because of the low number of recorded stillbirths (n = 1,237), the estimated effects of
the different age classes were relatively small.
(age class) for the occurrence of stillbirth in the two different models
Age class
n
Model 1*
Model 2**
LSQ
LSQ
s.e.
s.e.
26,774
0.024 ± 0.003
0.025 ± 0.003
29,936
0.026 ± 0.003
0.027 ± 0.003
18,064
0.028 ± 0.003
0.029 ± 0.003
7,001
0.035 ± 0.004
0.037 ± 0.004
Outcome of season’s first mating
A total of 127,684 matings were recorded as first inseminations within the respective
season. Almost one fifth (18.5%) of these coverings was successful.
A significant influence of inbreeding was detected (p ≤ 0.05) in Model 1 (inbreeding
coefficient of the mare). The linear regression coefficient was positive at a value of
0.34 ± 0.05. A one per cent increase in the mares’ inbreeding coefficient increased
the probability of a successful first mating by 0.03%.
58
No significant impact of inbreeding was detected in Model 2 (inbreeding coefficient of
the expected foal). The age of the mare at mating affected the outcome of the
season’s first mating in a significant way in both of the models used
(p ≤ 0.001, Table 3). Age class 1 (mares at the age of five years and younger) was
found to be the subset with the highest value for the outcome of the season’s first
mating. A mean value of 0.402 ± 0.024 was computed for this subset of mares
(Model 1, Table 3). Broodmares older than 16 years of age were detected to have the
lowest
first
insemination
success
at
a
mean
value
of
0.291
±
0.020
(Model 1, Table 3).
(age class) for the outcome of the season’s first mating in the two different models
Age class
n
Model 1*
Model 2**
LSQ
LSQ
s.e.
s.e.
39,587
0.402 ± 0.024
0.396 ± 0.023
44,546
0.374 ± 0.023
0.360 ± 0.022
29,853
0.339 ± 0.022
0.324 ± 0.021
13,698
0.291 ± 0.020
0.275 ± 0.019
Variance components and heritability
The heritability for the foaling rate was estimated at 0.024 in Model 1 (inbreeding
coefficient of the mare) when the dam was used as the basic individual. If the foal
was taken as the animal under study (Model 2, inbreeding coefficient of the expected
foal), the value rose to 0.033 (Table 4). For the occurrence of stillbirth, the value of
heritability decreased from 0.069 (Model 1) to 0.008 in Model 2. With a value of
59
0.059, the heritability of the outcome of the season’s first insemination was slightly
higher if the mare was the focused animal than with the expected foal being the
observed individual (h2 = 0.054, Table 4). With exception of the occurrence of
stillbirth, the permanent environmental effect of the sire was always found to be
higher than the permanent environmental effect of the dam, whether the mare
(Model 1) or the expected foal (Model 2) was used as the basic individual (Table 4).
Table 4 Variance components of random effects for different traits
Trait
Stallion
Mare
Add. genetic (mare/foal)
/
h2
/
Model 1 (Mare as basic individual)
Foaling rate
0.422
± 0.0261)
0.109
± 0.006
0.051
± 0.006
0.013
± 0.001
0.096
± 0.008
0.024
± 0.002
Stillbirth
0.028
± 0.019
0.0069
± 0.005
0.356
±0.133
0.089
± 0.031
0.274
± 0.103
0.069
± 0.025
First mating
outcome
1.091
± 0.067
0.233
± 0.011
< 0.001
± 0.000
0.279
± 0.016
0.059
± 0.003
< 0.001
± 0.000
Model 2 (Expected foal as basic individual)
Foaling rate
0.409
± 0.026
0.109
± 0.006
0.087
± 0.005
0.023
± 0.003
0.129
± 0.014
0.033
± 0.003
Stillbirth
0.025
± 0.026
0.006
± 0.006
0.572
± 0.112
0.146
± 0.025
0.033
± 0.090
0.008
± 0.022
0.219
± 0.011*
0.116
± 0.016
0.024
± 0.003
0.254
± 0.033
0.054
± 0.007
First mating 1.039
outcome
± 0.068
1)
= s.e.
The largest sire effect was estimated for the outcome of the season’s first mating with
a proportion of 0.219 in Model 1 whereas the dam effect for this trait was close to
zero (Table 4). In the case of the occurrence of stillbirth, higher values were observed
for the permanent environmental effect of the dam (Model 1 and Model 2) compared
to the values for the sire. It rose from 0.089 in Model 1 to 0.147 in Model 2 (Table 4).
60
The sire effect (0.006) did not change, whether the mare or the expected foal was
used as the observed individual. For all other traits, the dam effect was always
estimated at below 0.0025, unaffected by the model used (Table 4).
Discussion
Data recording and investigated traits
Some problems concerning the recording of fertility and reproductive health could be
addressed during the analysis of mating and foaling data to determine the factors
which influence female fertility in Holstein horses.
As a primary source of information, written reports of foalings (sent in by breeders)
are used by breeding associations to complete their database during breeding
season. A written report of a foaling is mandatory for the breeders to achieve
registration of their foals. However, the mandatory part of that foaling report regards
information of a more general nature (e.g. date of foaling, place of foaling, parents,
markings and sex of the foal). Further important questions concerning health, fertility
and particularly on fertility disorders such as stillbirth and twinning are asked but their
response is not obligatory (see also: Dohms, 2002). Some horse breeders may be
afraid of personal consequences if fertility problems concerning are reported
(Hartig et al., 2013). Against this background, it is possible to explain the low number
of observations for twinning (n = 96) and stillbirth (n = 1,237) within this comparatively
large dataset (overall n = 379,458). It might be reasonably assumed that there is a
high incidence of unreported cases of serious kinds of fertility disorders. Hence, it
might be difficult to measure reproductive performance and health in a given
breeding stock precisely. There is a need to specify data recording and to generate
more comprehensive information (stillbirth, twinning, early abortion etc.) concerning
61
noteworthy findings which could influence equine reproductive performance
(Wilkens, 1989; Dohms, 2002).
Another problem of data recording is that only the last mating date of a mare is
mandatory on the foaling report. All other prior insemination dates are sent to the
breeding association by stallion stud to prove that the semen has been used
properly. Only if there is a live-born and registered foal is a mating clearly coded as
successful. But, many of the mares are inseminated in more than one cycle during a
season because of unsuccessful prior matings. It is possible that one or more of
these prior matings was followed by fertilisation, but the pregnancy was not detected
or even interrupted in a very early state (e.g. absorption). Without any recorded
finding of prior pregnancy examinations, there is no clear evidence of the result of a
single insemination (e.g. conception or not). Therefore, the foaling rate (analysed as
individual outcome of a mating, 0/1) was used for the analysis instead of the
pregnancy or conception rate. For future research, it would be useful to record all
results of every pregnancy examination during the breeding season (e.g. to quantify
embryonic loss).
One important difference between the “classical” foaling rate (ratio foaled
mares/covered mares) and its individual equivalent (individual mating outcome, 0/1)
is that the individual approach simultaneously allows statements regarding the
number of inseminations needed to produce a foal (Wilkens, 1989). In compliance
with various environmental management factors, beside female fertility, this measure
is equally suitable to evaluate male reproductive performance (Wilkens, 1989).
The occurrence of stillbirth was included in the present study on Holstein Warmblood
horses motivated by research projects on stillbirth and foetal loss depending on the
amount of inbreeding in dairy cattle (Hinrichs and Thaller, 2011; Van Raden and
Miller, 2006). Although the number of observations in the current dataset was
62
comparatively low, the findings in cattle gave rise to the presumption that increased
inbreeding in the mare or progeny affected the occurrence of stillbirth in horses. Prior
studies on stillbirth in horses have merely focused on the non-genetic causes of this
kind of fertility disorder (Giles et al., 1993; Hong et al., 1993; Smith et al., 2003;
Marenzoni et al., 2012). Until now, investigations into the genetic impact on stillbirth
in horses have not been performed.
Additionally, the impact of environmental management and farm factors must be
assumed when studying equine reproductive performance (Bruns et al. 1983; Nissen,
1986; Dohms, 2002; Wilkens, 1989). In line with the studies of Dohms (2002),
Langlois and Blouin (2004) and Sairanen et al. (2009), this work also detected
environmental impacts (e.g. age of the mare at mating) on the investigated fertility
traits. The inclusion of the farm as a random effect (farm identification number) was
tested in the current study, but all estimated values during the analysis of variance
were close to zero. Presumably, the farm effect is mapped by the environmental
effect of the mare, because of comparatively low herd sizes (fewer than three mares
per breeder). To obtain conclusive statements about the impact of operational
management factors, a classification of the farms by quality defining factors
(e.g. professional qualification of the farm manager) is recommended (Dohms, 2002).
This kind of data was not available for the present research project.
Impact of inbreeding on female fertility traits
Fitness-associated fertility traits with low heritability are generally more sensitive to
be affected by increased inbreeding because of weakly pronounced dominant gene
effects(Charlesworth and Charlesworth, 1987; Falconer and Mackay, 1996; Hansson
and Westerberg, 2002). Previous studies which detected an impact on increased
inbreeding on female fertility in horses confirmed this statement and reported
63
decreasing fertility trends (Cothran et al., 1984; Langlois and Blouin, 2004).
Conversely, Cothran et al., (1984) identified the positive effects of inbreeding on
fertility in Standardbred trotters as opposed to pacers. Also in the present study,
slightly positive effects of increased mare inbreeding on the individual outcome of a
mating and on the success of the first mating per mare and season were found.
In scientific literature, positive inbreeding effects on fertility are rare. Shields (1982)
originally called this phenomenon “inbreeding enhancement”. Lacy et al. (1996) and
Margulis (1998) found a positive effect of dam inbreeding on offspring viability in a
subspecies of mice. Furthermore, Ballou (1997) observed a significantly positive
effect of maternal inbreeding on neonatal survival in European bison. This increase in
fitness is probably due to the fixation of favourable gene complexes or epistatic
relationships (Templeton, 1979). On the other hand, “outcrossing” does not always
enhance fitness. Crosses between distant populations of the same species
sometimes lead to significant outbreeding depression (Köck et al., 2009). The decline
in reproductive fitness under outcrossing is usually attributed to a break up of coadapted gene complexes or favourable epistatic relationships (genetic incompatibility,
Falconer and Mackay, 1996). Like crossbreeding not always has beneficial effects on
fitness, inbreeding is not always detrimental (Köck et al., 2009).
The influence of inbreeding on fertility disorders in horses, such as twinning, stillbirth,
retained placenta or early abortion were previously investigated by Klemetsdal and
Johnson (1989), Sevinga et al. (2004) and Wolc et al. (2006). The authors found
detrimental effects of inbreeding on the occurrence of retained placenta in Frisian
horses (Sevinga et al., 2004) and on early abortion in Norwegian Trotters,
respectively (Klemetsdal and Johnson, 1989). Sevinga et al. (2004) assumed the
frequency of retained Placenta in Frisian horses as a trait of the expected foal.
Increased mare inbreeding did not affect the incidence of the trait (Sevinga et al.,
64
2004). The incidence for retained placenta in Frisian horses after normal foaling was
estimated at 54% (Sevinga et al., 2004). Reversely, Klemetsdal and Johnson, (1989)
defined the frequency of early abortion in Norwegian Trotters as a trait of the mare.
No inbreeding effect was found using the inbreeding coefficient of the expected
offspring (Klemetsdal and Johnson, 1989). In the present study, a significantly
negative impact of increased foal inbreeding on the occurrence of stillbirth in Holstein
warmblood Horses was detected. A research project on inbreeding effects on calving
traits in dairy cattle (Hinrichs et al., 2011) confirmed this result. The rate of stillbirth in
dairy cows was estimated at 8.19% and the risk of stillbirth was found to increase by
0.22% per 1% increase of the inbreeding coefficient of the calf (Hinrichs et al., 2011).
Previous studies by Mc Parland et al. (2007) on Irish Holstein–Friesian dairy cattle
showed an increased incidence of stillbirth in primiparous animals at a rate of 0.20%
± 0.04% per 1% increase in inbreeding. Additionally, van Raden and Miller (2006)
reported increased inbreeding of cattle embryos having negative effects on
conception and the survival of the embryo. Therefore, Hinrichs et al. (2011) stated
that it is not surprising when increased inbreeding also results in an increased risk of
stillbirth if inbreeding has negative effects on conception and the survival of the
embryo. A similar situation in horses is quite conceivable, but corresponding studies
are lacking.
Variance components and heritability
In agreement with common literature, the values of heritability for all considered
fertility traits were calculated at a low level, .i.e. less than 10%. When the foal was
used as the basic individual (Model 2), heritability is nearly similar to the value of
3.5% estimated by Wilkens (1989) in the case of the foaling rate. If the inbreeding
coefficient of the mare was integrated into the model, the value was lower. Sairanen
65
et al. (2009) also detected higher heritability estimates for the individual foaling rate if
the foal was the studied animal. They suggest that they were then accounting for all
three sources of genetic variation on fertility (mare, stallion and foal) (Sairanen et al.,
2009). Reversely, the present heritability estimates for the occurrence of stillbirth
(h2 = 0.008) declined if stillbirth was treated as a foal trait (Model 2). If the same
phenotype is assumed as a trait of the mare, the value (h2 = 0.069) is in the range of
estimates for other fertility disorders such as early abortion (h2 = 0.05, Klemetsdal
and Johnson, 1989). Estimating heritability for stillbirth in cattle, Hinrichs et al. (2011)
computed a value of h2 = 0.05, modelling the inbreeding coefficient of the calf.
The values did not change remarkably concerning the heritability estimates for the
outcome of the first mating per mare and season, depending on the model used.
Excluding the occurrence of stillbirth, the stallion explained a greater part of total
variance of the traits studied. For the frequency of stillbirth, the impact on total
variance of the mares’ permanent environment is greater, independent of the model
utilised. This is in contrast to Sairanen et al. (2009). They represented the dam
explaining the greater part of total variance of the foaling rate in all of their different
models (Sairanen et al., 2009).
Conclusion
The inbreeding coefficients for the whole Holstein horse population as well as for the
subsets of mares and foals analysed are estimated at a moderate level. It has been
demonstrated that increased inbreeding does not lower female fertility traits such as
the individual mating outcome or the outcome of the season’s first mating for this
breed, irrelevant of whether they are modelled as a trait of the mare or the expected
foal. Despite the low number of recorded phenotypes, the frequency of stillbirth is
66
affected by increased foal inbreeding in a significantly negative way. The values of
heritability for all of the traits studied are calculated at a low level, with a declining
trend for the frequency of stillbirth if it is modelled as a trait of the expected foal. The
results give cause for further investigations especially on the impact of increased
inbreeding on the occurrence of some more fertility disorders (e.g. early abortion and
twinning) in horses. For this kind of research, the largest possible number of high
quality phenotypes is required. Therefore, it is advisable to improve the recording of
fertility and its disorders in horses. To avoid an increase in the frequency of fertility
disorders and to maintain long-term fertility performance, matings of closely related
parents should be avoided.
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Hartig, W., H. Houe, and P. H. Andersen. 2013. Monitoring of equine health in
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W. Roberts, B. J. Smith, R. R. Tramontin, P. A. Tuttle, and T. W. Swerczek. 1993.
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71
CHAPTER FOUR
Standardisierte Erfassung von Gesundheitsdaten
beim Holsteiner Pferd
L. Roos und J. Krieter
Institut für Tierzucht und Tierhaltung, Christian-Albrechts-Universität, Kiel, Deutschland
72
Zusammenfassung
Innerhalb der deutschen Pferdezucht wird derzeit noch keine standardisierte und
flächendeckende Erfassung von Gesundheitsdaten praktiziert. Die Einführung neuer
Selektionsstrategien (genomische Selektion) sowie eine angespannte Marktlage
machen
jedoch
eine
Anpassung
der
Zuchtprogramme
hinsichtlich
der
Berücksichtigung funktioneller Merkmale sowie eine Optimierung der Abläufe im
praktischen Zuchtbetrieb nötig. Im Rahmen einer Feldstudie zur Erfassung von
Gesundheitsdaten beim Holsteiner Pferd wurde die aktuelle Datenlage in Bezug auf
funktionelle
Merkmale
sowie
die
grundsätzliche
Durchführbarkeit
eines
Gesundheitsmonitorings untersucht. Projektziel war die modellhafte Entwicklung
einer Datenbank zur einheitlichen Speicherung und Auswertung von Diagnosedaten
aus der tierärztlichen Praxis. Die Qualität der zur Verfügung gestellten Daten lässt
Handlungsbedarf
erkennen,
Gesundheitsdaten
zurückgegriffen
Tierarztpraxen
(n=11)
sofern
stellten
in
Zuchtprogrammen
zukünftig
soll.
Die
Hälfte
der
beteiligten
Diagnosedaten
der
von
ihnen
betreuten
werden
auf
Stutenbestände zur Verfügung. Die vorliegenden Informationen wurden uneinheitlich
und meist handschriftlich erfasst. Ein nachvollziehbarer Bezug zwischen Diagnose
und Einzeltier (über die Lebensnummer) war nur für wenige Stuten innerhalb der
Datenbank gegeben. Die nachträgliche Kategorisierung der Informationen über ein
im Vorfeld entwickeltes Schlüsselsystem war auf Grund der großen Unterschiede
zwischen
den
einzelnen
Dokumentationsschemata
kaum
möglich.
Eine
epidemiologische Auswertung bezüglich Inzidenzen und Prävalenzen bestimmter
Krankheitsgeschehen konnte nicht durchgeführt werden. Die effiziente Nutzung
veterinärmedizinscher Daten innerhalb von Zuchtprogrammen wird zukünftig jedoch
nur über ein standardisiertes und allgemein gültiges Erfassungssystem sowie einen
einfachen, zentral geregelten Datentransfer möglich sein.
73
Abstract
Standardised health recording is not currently performed in German horse breeding
programs. However, the introduction of new selection strategies (genomic selection)
requires the adjustment of breeding schemes regarding the consideration of health
recordings. The current data situation as well as the fundamental feasibility of health
monitoring was checked during a field study to assess veterinary data on Holstein
Warmblood horses. The aim of the study was to develop a model-like database for
consistent storage and evaluation of veterinary diagnostic information.
The quality of the data submitted needs improvement if breeding organisations intend
to rely on veterinary records in the future. 50% of the veterinarians involved (n=11)
provided data on the broodmare stock served by them. Their recordings were
characterised by the inconsistent use of symbols and abbreviations and mostly
handwritten. A direct relation between one record and a single broodmare (by Unique
Equine Live Number, UELN) was given for only a small number of animals. A
subsequent categorisation of recordings by a specially developed key system could
not
be
performed
because
of
the
different
documentation
schemes.
An
epidemiological evaluation regarding incidence and prevalence of special diseases
was not possible. For a sustainable and efficient use of veterinary data, breeding
organisations are called upon to establish generally consistent monitoring systems as
well as simple and centrally controlled data transfer solutions.
74
Einleitung
Gesundheit und Fruchtbarkeit spielen in der Pferdezucht eine überragende Rolle.
Beide Faktoren beeinflussen das Wohlbefinden der Tiere und den wirtschaftlichen
Erfolg eines Zuchtbetriebes erheblich (Dohms, 2002; Wilkens 1989). Voraussetzung
für eine züchterische Bearbeitung von funktionalen Merkmalskomplexen innerhalb
von Zuchtprogrammen ist jedoch eine zuverlässige und einheitliche Erfassung des
Phänotyps (Egger-Danner, 2012). Zusätzlich ist die Dokumentation von betrieblichen
Kenngrößen zu Haltung und Management erforderlich, da sowohl die Fruchtbarkeit
als auch die allgemeine Tiergesundheit unmittelbar von den Gegebenheiten und
Abläufen im betrieblichen Umfeld beeinflusst werden. Neben einer züchterischen
Nutzung solcher Daten bietet sich deren Verwendung im Rahmen einer
betriebsspezifischen
Züchterberatung
von
Seiten
der
Zuchtverbände
an
(Roos, 2010). Eine flächendeckende, standardisierte Phänotypisierung mit zentraler
Datenverwaltung und -auswertung ist derzeit in der deutschen Pferdezucht jedoch
nicht gegeben. Es fehlen einheitliche Diagnoseschlüssel zur Erfassung von
Diagnosen im Rahmen der veterinärmedizinischen Praxis. Die Dokumentation erfolgt
uneinheitlich
und
nicht
immer
in
EDV-gestützter
Form.
Eine
zentrale,
praxisübergreifende Auswertung wird somit zusätzlich erschwert. Die Integration von
Gesundheitsmerkmalen in die Zuchtarbeit, im Hinblick auf die Schätzung von
Gesundheitszuchtwerten und die Einführung der genomischen Selektion ist derzeit
nur indirekt über Hilfsmerkmale (Exterieur, Leistung) möglich (Koenen et al., 2004;
Nikolić, 2009). Ziel dieser Studie war daher die erstmalige, modellhafte Entwicklung
und Erprobung eines standardisierten Monitoringsystems zur zentralen Auswertung
von
Gesundheits-
und
Fruchtbarkeitsdaten
am
Beispiel
ausgewählter
Pferdezuchtbetriebe in Schleswig–Holstein in Zusammenarbeit mit den jeweiligen
Bestandstierärzten.
75
Im Fokus stand weiterhin die Erarbeitung eines einheitlichen Diagnoseschlüssels zur
Kategorisierung und Standardisierung der Daten. Zusätzlich sollten betriebliche
Informationen zu Haltung und Fütterung mittels Fragebogen erfasst werden um eine
Quantifizierung
des
Umwelteinflusses
auf
ausgewählte
Gesundheits-
und
Fruchtbarkeitsparameter zu ermöglichen.
Material und Methoden
Beteiligte Betriebe
Die Standorte der einzelnen Kooperationsbetriebe erstreckten sich über alle
Körbezirke des Verbandes der Züchter des Holsteiner Pferdes e.V. innerhalb
Schleswig-Holsteins. Bedingung zur Teilnahme war ein Stutenbestand von mehr als
10 zuchtaktiven Tieren. Es folgte die zufällige Auswahl von 120 Pferdezuchtbetrieben
aus dem Mitgliederbestand des Holsteiner Verbandes, Abteilung Zucht in Kiel. An der
Datenerfassung im Feld beteiligten sich schließlich 29 Zuchtbetriebe mit insgesamt
557 beim Verband der Züchter des Holsteiner Pferdes registrierten Zuchtstuten. Über
die teilnehmenden Pferdezuchtbetriebe wurden die jeweiligen Bestandstierärzte
(22 Tierarztpraxen)
bezüglich
einer
einzeltierbezogenen
Datenübermittlung
kontaktiert. Im Rahmen eines persönlichen Gespräches wurden sowohl Züchter und
Besitzer der Stuten, als auch die Veterinäre bezüglich der Ziele und Inhalte des
Projektes informiert. Die Freigabe der Daten erfolgte durch den Stutenbesitzer. Zu
Beginn der Studie im Jahr 2011 waren alle tierärztlichen Praxen zu einer Kooperation
bereit. Die Stammdaten der einzelnen Betriebe wurden in eine Datenbank
aufgenommen und jeweils mit einer einmalig vergebenen Identifikationsnummer (ID)
versehen.
76
Stutenspezifische Daten
Um eine möglichst eindeutige Zuordnung der Daten zu gewährleisten, wurde von
jedem Betrieb eine Bestandsliste bestehend aus der Lebensnummer, dem Namen,
dem Geburtsdatum und der Stammnummer jeder Stute erstellt. Für eine feste
Verbindung zwischen Stute und Betrieb wurde jeder Stutendatensatz innerhalb der
Datenbank mit der jeweiligen Betriebs-ID verknüpft.
Diagnoseschlüssel
Zur Sicherstellung eines Standards bei der Dokumentation von tierärztlichen
Diagnosen
wurde ein Diagnoseschlüssel entwickelt. Die Codierung der Befunde
folgte einer übergeordneten Gruppierung und Nummerierung nach Organsystemen.
Die Festlegung und Einteilung der übergeordneten Organsysteme erfolgte mit Hilfe
entsprechend gegliederter Fachliteratur (Wintzer et al., 1999) und unter Rücksprache
mit einem entsprechend qualifizierten Fachtierarzt für Pferde (Dr. K. Blobel,
Ahrensburg). Innerhalb der Organsysteme wurden Untergruppen gebildet, welche
wiederum durchnummeriert und in einzelne Krankheitsbilder unterteilt wurden (siehe
Anhang A1). Sollte die Befunderhebung Krankheitsbilder ergeben, welche nicht
innerhalb einer Über- oder Untergruppe codiert sind, besteht innerhalb jedes
Organsystems in der Untergruppe „Sonstiges“ die Möglichkeit zur Ergänzung der
entsprechenden Diagnose. Eine dynamische Weiterentwicklung des Systems bleibt
auf diese Weise gewährleistet.
Daten zu Haltung, Fütterung und Management
Zur Erfassung von Informationen zu Haltung, Fütterung und Management der Stuten
wurde auf jedem der beteiligten Betriebe im Rahmen von Betriebsbesuchen (ab
Januar 2012) ein Betriebsfragebogen ausgefüllt.
77
Auf dem Zuchtbetrieb wurde neben den betrieblichen Stammdaten und der
Qualifikation des Betriebsleiters, die Art der Aufstallung (Einzel- /Gruppenbox,
Offenstall, Laufstall), die vorhandene Auslauf-/Weidefläche, Art und Dauer der
Auslaufgewährung
sowie
Fragen
zur
Fütterung
und
zum
Zucht-
und
Hygienemanagement (Impfung/Entwurmung, Hormoneinsatz, Art der Besamung etc.)
geklärt. Die Dokumentation der Gegebenheiten auf den Betrieben erfolgte mit Hilfe
einer
Checkliste,
welche
auf
Grundlage
des
Bewertungskonzeptes
für
pferdehaltende Betriebe nach Beyer (1998) erstellt wurde (siehe Anhang A2).
Tierärztliche Diagnosen und Behandlungen
Alle Bestandstierärzte wurden gebeten, sämtliche Diagnose- und Behandlungsdaten
(Fruchtbarkeit und allgemeine Gesundheit) der zurückliegenden zwei Kalenderjahre
(2010 und 2011) zu allen Stuten des von ihnen betreuten Zuchtbetriebes mit
möglichst eindeutigem Einzeltierbezug (Lebensnummer) einzusenden. Zur internen
Erprobung des beschriebenen Diagnoseschlüssels sollten diese Daten nachträglich
von Hand eingruppiert und in die Datenbank eingepflegt werden. Danach war die
routinemäßige Anwendung und Erprobung des Schlüsselsystems im Feld durch
ausgewählte Tierärzte auf den jeweiligen Kooperationsbetrieben geplant.
Ergebnisse und Diskussion
Betriebliche Daten und Bestandslisten
Von den insgesamt 29 beteiligten Zuchtbetrieben sendeten 25 Züchter (86,2%)
vollständig ausgefüllte Betriebsfragebögen ein. 20 Zuchtbetriebe (68,9%) waren
bereit, eine vollständige Liste aller zuchtaktiven Stuten mit deren Lebensnummer zur
Verfügung zu stellen.
78
Von der zu erwartenden Mindestzahl von 557 zuchtaktiven Stuten konnten somit
339 Zuchttiere (60,8%) in die Datenbank aufgenommen werden. Als überwiegende
Form der Aufstallung wurde die Haltung der Stuten in Einzelboxen praktiziert
(75% der Betriebe). Die Größe der Einzelboxen entsprach auf allen Betrieben den
Leitlinien zur Beurteilung von Pferdehaltungen unter Tierschutzgesichtspunkten des
Bundesministeriums
für
Ernährung,
Landwirtschaft
und
Verbraucherschutz
(BMELV, 2009) von ≥ (2xWiderristhöhe)2. Alle Zuchtbetriebe gewährten den Stuten
ganzjährig, täglichen Auslauf in Gruppen bei ausreichender Flächenausstattung.
Grundsätzlich war die Zusammenarbeit mit Tierärzten und Züchtern in SchleswigHolstein von großem Interesse geprägt. Allerdings zeigt die Tatsache, dass nicht alle
Pferdezüchter bereit waren, Informationen zu ihrem Tierbestand zur Verfügung zu
stellen, eine gewisse Skepsis gegenüber dem Informationsaustausch. Da das
Einverständnis des jeweiligen Stuteneigentümers zur Datenweitergabe jedoch
zwingend erforderlich ist, sollte in Zukunft bestmögliche Aufklärungsarbeit seitens der
Verbände betrieben werden, um Bedenken auszuräumen (Hartig et al., 2013). Im
Rahmen der Entwicklung einer Datenbank sind klar definierte Zugriffs- und
Nutzungsrechte bezüglich der bereit gestellten Daten zu beachten und gelten als
eine notwendige Grundvoraussetzung (Egenvall et al., 2011, Hartig et al., 2013).
Eine Erhöhung der Motivation seitens der Pferdezuchtverbände über finanzielle
Anreize ist bei knapper werdenden Mitteln meist schwer zu leisten, könnte jedoch
(z.B. über Nachlässe bei regelmäßig anfallenden Gebühren) zu einem höheren
Datenaufkommen von Seiten der Züchter führen (korrekte Fohlenmeldung, Angabe
von Totgeburten etc.).
79
Diagnose- und Behandlungsdaten
Die Erfassung tiermedizinischer Daten im Verlauf des dargestellten Modellprojektes
für die Pferdezucht verdeutlichte, dass die bisher vorhandene Datengrundlage
bezüglich ihrer Qualität und Quantität nicht ausreicht, um sie sowohl züchterisch als
auch im Sinne der Optimierung von Managementabläufen im praktischen
Zuchtbetrieb zu nutzen. Der Datenrücklauf bezüglich Diagnosedaten der beteiligten
Bestandstierärzte war nicht zufriedenstellend.
Elf von 22 kooperierenden Tierarztpraxen übersendeten Datensätze zu ihrer Tätigkeit
auf den betreuten Zuchtbetrieben. Es handelte sich hierbei ausschließlich um
Befunde und Behandlungen aus den Bereichen Gynäkologie und Reproduktion. Die
Art und Weise der Aufzeichnung (z.B. Ovarbefunde) unterschied sich zwischen den
Veterinären bezüglich der verwendeten Symbolik und den genutzten Abkürzungen
erheblich. Die manuelle oder sonographische Befunderhebung im Verlauf von
Trächtigkeitsuntersuchungen
erfolgte
handschriftlich
ohne
Dokumentation.
und
Eine
meist
nachträgliche
wenig
direkte
standardisiert,
Nutzung
elektronische
einer
vielfach
noch
EDV-gestützten
Speicherung
sowie
eine
standardisierte Kategorisierung mittels Diagnoseschlüssel durch Dritte erwiesen sich
als
nicht
durchführbar.
Diagnosen
bezüglich
der
allgemeinen
Gesundheit
(Bewegungs- und Atmungsapparat, Verdauungstrakt etc.) wurden nicht übermittelt
oder waren nicht ausreichend dokumentiert.
Ein nachvollziehbarer Einzeltierbezug bezüglich einer vorhandenen Diagnose oder
Behandlung war für lediglich 150 Stuten (44,2% des Stutenbestandes in der
Datenbank) gegeben. Eine logische Verknüpfung von Informationen innerhalb der
Datenbank als Basis für die Verarbeitung und Auswertung war so nur eingeschränkt
gegeben.
80
Erfahrungen
bei
anderen
Spezies
zeigen,
dass
gerade
im
Hinblick
auf
Gesundheitszuchtwerte eine vertrauenswürdige und in sich logische Datengrundlage
von entscheidender Bedeutung ist (Egger-Danner et al, 2010, Egenvall et al., 2011).
Möglichkeiten
zur
technischen
Umsetzung
eines
Erfassungssystems
für
Gesundheitsdaten sind über die Rinderzucht bereits gegeben (vgl. Egger-Danner et
al., 2012, Koeck et al., 2012, Stock et al., 2012) und müssen für die Pferdezucht
nicht neu entwickelt werden. Sowohl in Deutschland als auch in Österreich haben
sich mehrere Systeme zum Monitoring von Diagnosen und Behandlungen
(ProGesund, GKuh etc.) etabliert. Erstmals im Jahr 2008 wurden in Österreich
Prävalenzen und Inzidenzen für Eutererkrankungen bei Fleckvieh und Braunvieh zur
Verfügung gestellt (Obritzhauser et al. 2008, Schwarzenbacher et al., 2010). Im Jahr
2013 wurden in Österreich erste Gesundheitszuchtwerte für das Braunvieh
veröffentlicht. In Skandinavien wird die direkte Erfassung und Auswertung von
Tiergesundheitsdaten bei Rindern bereits seit einiger Zeit praktiziert (z.B. Østerås &
Sølverød, 2005). In Norwegen konnte durch eine gezielte züchterische Nutzung der
Daten eine Senkung des statistischen Erkrankungsrisikos für Mastitis beobachtet
werden (Østerås & Sølverød, 2005).
Eine dänische Forschungsgruppe überprüfte mittels Befragung, die Bereitschaft
verschiedener Akteure des Pferdesektors zur Weitergabe von Daten sowie Fragen
zur Einrichtung und Finanzierung einer Gesundheitsdatenbank für Pferde (Hartig et
al., 2013). Die Mehrheit aller Befragten (86%) war hier grundsätzlich bereit, sich mit
eigenen
Daten
zu
beteiligen,
sofern
Bedenken
bezüglich
Datensicherheit,
Datenbesitz und Zugangsrechten ausgeräumt werden können (Hartig et al., 2013).
Eine Befragung unter Holsteiner Pferdezüchtern zur Akzeptanz externer Beratung
zeigte eine große Aufgeschlossenheit der Züchterschaft (Roos, 2010).
81
92 % der befragten Züchter (n=82) befürworteten ein Beratungsangebot und die
damit verbundene Weitergabe betrieblicher Daten. Unabhängig von der Größe des
Betriebes würde sich die Mehrheit der Pferdezüchter (76%) eine intensivere
Beratung seitens der Tierärzte wünschen (Roos, 2010). In einem im Jahr 2013
initiierten Gemeinschaftsprojekt wird nun auch in Deutschland versucht, einen
Zuchtverbandsübergreifenden Ansatz zur Entwicklung einer Gesundheitsdatenbank
für Pferde zu verfolgen (Sarnowski et al., 2013).
Ausblick
Neben direkten Einflüssen von Gesundheit und Fruchtbarkeit auf das Wohlergehen
des Pferdes und den ökonomischen Erfolg eines Zuchtbetriebes verlangt der Käufer
nach Zuchtprodukten von optimaler gesundheitlicher Entwicklung. Dem hohen
Kapitaleinsatz entsprechend sieht sich die Pferdezucht einem erheblichen Preisdruck
ausgesetzt (Fuchs, 2014). Optimierte Zuchtprogramme sowie eine ständige Kontrolle
des
Bestands-
und
Datenmanagements
von
Seiten
der
Züchter
und
Bestandstierärzte bieten Vorteile bei Marktpositionierungen und können dazu
beitragen, die Wirtschaftlichkeit des Unternehmens zu erhalten (Niemann, 2014).
Durch
die
Einführung
eines
einheitlichen
Gesundheitsmonitorings
können
flächendeckend standardisierte Phänotypen zur Anpassung der Zuchtprogramme in
Bezug auf neue Merkmale und Zuchtstrategien (genomische Selektion) generiert
werden. Von Seiten der Zuchtorganisationen sollte außerdem eine eindeutige
Erfassung
und
Aufklärung
von
Erbfehlern
sowie
die
Sicherstellung
von
entsprechendem Probenmaterial angestrebt werden (Tetens, 2014). Das von einigen
deutschen Pferdezuchtverbänden bereits angewendete System der linearen
82
Beschreibung des Exterieurs bietet hier zusätzliche Möglichkeiten der direkten
Erfassung von für die Tiergesundheit relevanten Phänotypen (Duensing et al., 2014).
Eine integrierte Ausgabe von Gesundheitsberichten für Tierärzte und Züchter kann
Optimierungsprozesse sowohl innerhalb des Zuchtbetriebes als auch bezüglich der
tierärztlichen Praxisroutine erleichtern (Egger-Danner, 2010; Abbildung 1).
Abbildung 1: Flussdiagramm eines Monitoringsystems für Gesundheits- und
Managementdaten aus der Pferdezucht (nach Egger-Danner, 2010, verändert)
Zielsetzung sollte eine umfassende Datenerhebung in Bezug auf möglichst viele
Krankheitsgeschehen unter Ausnutzung aller möglichen Vernetzungsmöglichkeiten
zwischen den Akteuren sein (Egenvall et al., 2011). Der durch ein solches System zu
generierende Nutzen kann entscheidend zu einer Erhöhung der Akzeptanz von
Seiten der Züchter und Tierärzte beitragen und muss seitens der beteiligten
Zuchtorganisationen kommuniziert und beworben werden. Ein nachhaltiger Nutzen
83
kann allerdings erst im Verlauf der Umsetzung, aufbauend auf den bereitgestellten
Daten entwickelt werden (Egger- Danner et al., 2010, Egenvall et al., 2011). Zudem
sind umfassende Information und Aufklärung der Züchterschaft wie auch Schulungen
für Tierärzte im Hinblick auf die Anforderungen bezüglich Dokumentation und PraxisEDV erforderlich.
Von größter Bedeutung für die Effizienz eines Monitoringsystems ist die absolut
einheitliche Erfassung der Daten nach einem allgemein gültigen Schlüssel (Egenvall
et
al.,
2011).
Nicht
zuletzt
muss
Eingabemöglichkeiten,
unter
Einbindung
Zugangsrechten
unter
Wahrung
und
über entsprechende
der
Schnittstellen
Praxis–EDV
größtmöglicher
bei
und
definierten
Datensicherheit,
ein
unkomplizierter Datentransfer ermöglicht werden. Es gilt, die bereits vorhandenen
Ressourcen in Bezug auf tierärztliche Datenverarbeitung optimal zu nutzen um
sowohl den zeitlichen als auch den finanziellen Mehraufwand für alle Beteiligten in
Grenzen zu halten. Neben flexiblen Schnittstellen mit hoher Kompatibilität zu
unterschiedlicher
Praxis-Software
könnten
auch
Webapplikationen
einfache
Möglichkeiten zur Erfassung, Speicherung und für den Transfer von Daten bieten.
Auf
diesem
Weg
kann
eine
nachhaltige
Nutzung
von
Diagnose-
und
Managementdaten zur züchterischen Verbesserung der Tiergesundheit und
Fruchtbarkeit erreicht werden. Zusätzlich würden sowohl Züchter als auch
Bestandstierärzte eine Möglichkeit zur Kontrolle und Optimierung betrieblicher
Abläufe im Rahmen des Bestandsmanagements und der Beratung erhalten.
84
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87
Anhang A1 Diagnoseschlüssel zur Erfassung von Gesundheitsdaten beim Pferd (Roos, 2011, unveröffentlicht)
Organsystem/Diagnose/Behandlung
3.4.
Leukozytenerkrankungen
1.
Schlüsselnr.
Haut
3.5.
Umfangsvermehrung der Milz
4.3.5.
Pleuritis
1.1.
nicht infektiöse Hautkrankheiten
3.6.
Sonstiges
4.3.6.
intrathorakale Neoplasien
1.2.
Verhornungsstörungen
4.4.
Pneumonie
1.3.
Tumoren der Haut
Atmungsorgane
4.4.1.
Pleurapneumonie des adulten Pferdes
1.4.
infektiöse Erkrankungen der Haut
4.1.
obere Atemwege einschl. Trachea
4.4.2.
Lungenabszess
1.5.
infektiöse Erkrankungen des Lymphapparates
4.1.1.
Atherom
4.4.3.
Rhodococcus- equi- Infektion
1.6.
Krankheiten der Unterhaut
4.1.2.
Rhinitis
4.4.4.
Aspirationspneumonie
1.7.
Sonstiges
4.1.3.
Sinusitis
4.4.5.
Mykotisch bedingte Pneumonie
4.1.4.
Gaumensegelverlagerung/ -veränderung
4.5.
Infektiöse Erkrankungen
4.
2.
Herz- Kreislaufsystem
4.1.5.
Erkrankungen der Rachenhöhle
4.5.1.
Pferdehusten
2.1.
Herzinsuffizienz
4.1.6.
Erkrankungen des Kehlkopfes
4.5.1.1.
Rhinoviren
2.2.
Herzklappenfehler
4.1.6.1.
Kehlkopfpfeifen
4.5.1.2.
Reoviren
2.3.
Kardiomyopathie
4.1.6.2.
Sonstiges
4.5.1.3.
Adenoviren
2.4.
Pericarderkrankung
4.1.7.
Erkrankungen der Luftsäcke
4.5.1.4.
Parainfluenza- 3- Viren
2.5.
Herzfrequenzstörung
4.1.8.
Erkrankungen der Trachea
4.5.2.
Pferdeinfluenza
2.6.
Herzrhythmusstörung
4.1.9.
Neoplasien der oberen Atemwege
4.5.3.
EHV I, II, IV
2.7.
Kongenitaler Herzfehler
4.2.
tiefe Atemwege und der Lunge
4.5.4.
Sonstiges
2.8.
Gefäßerkrankung
4.2.1.
COB
2.8.1.
Erkrankungen der Artherien
4.2.2.
Recurrent Airway Obstruction
5.
Mundhöhle, Zähne, Zunge und Kiefer
2.8.2.
Erkrankungen der Venen
4.2.3.
Sommerweide- assoziierte Atemwegsobstruktion
5.1.
gestörter Zahnwechsel
2.9.
Sonstiges
4.2.4.
Lungenemphyem
5.2.
abnorme Zahnanzahl
4.2.5.
Lungenwurminfektion
5.3.
Fehlstellungen
3.
Blut
4.2.6.
entzündliche Atemwegserkrankung
5.3.1.
Fehlstellungen der Kiefer
3.1.
Anämie
4.2.7.
belastungsinduziertes Lungenbluten
5.3.2.
Fehlstellungen der Zähne
3.1.1.
Blutungsanämie
4.2.8.
Lungenödem
5.4.
Zahnerkrankungen
3.1.2.
Hämolytische Anämie
4.3.
Pleura und Brusthöhle
5.4.1.
Pulpitis
3.1.3.
Funktionelle Anämie
4.3.1.
Pneumothorax
5.4.2.
Zahnfraktur
3.1.4.
Störungen der Erythropoese
4.3.2.
Flüssigkeit in der Pleurahöhle
5.4.3.
Zahnstein
3.2.
Erythrozytose
4.3.3.
Hydrothorax
5.5.
Parodontitis
3.3.
Störungen der Hämostase
4.3.4.
Phyothorax
5.6.
Stomatitis
88
5.7.
Abnorme Gebissabnutzung
8.1.3.
Magenüberladung primär/sekundär
8.16.2.
Tumoren
5.8.
Zementhypoplasie
8.1.4.
Chronische Magendilatation
8.16.3.
Sonstiges
5.9.
Karries
8.1.5.
Magenruptur
5.10.
Glossitis
8.1.6.
Magentumoren
9.
Leber
5.11.
Zungenlähmung
8.1.7.
Magenulzera
9.1.
spezifische akute Lebererkrankungen
5.12.
Tumoren
8.2.
Katarrhalische und entzündliche Erkrankungen des
Darmes
9.1.1.
Akute hepatische Nekrose
5.13.
Kieferfraktur
8.2.1.
Gastroduodenojejunitis (GDJ)
9.1.2.
Tyzzers Disease
5.14.
Sonstiges
8.2.2.
Typhlokolitis
9.1.3.
infektiöse Hepatitiden
8.2.3.
Sonstiges
9.1.4.
Bakterielle Hepatitis
6.
Kaumuskeln, Kiefergelenk, Speicheldrüse,
Zungenbein
8.3.
Magen- Darm Koliken
9.1.5.
akute toxische Hepatosen
6.1.
Erkrankungen der Kaumuskeln
8.3.1.
Spastische Kolik
9.1.6.
Leberlipidose
6.2.
Krankheiten des Kiefergelenks
8.3.2.
Meteorismus
9.2.
spezifische chronische Lebererkrankungen
6.3.
Krankheiten der Speicheldrüse
8.4.
Obstipation
9.2.1.
Chronische Leberzirrose
6.4.
Krankheiten des Zungenbeins
8.5.
Darmverlegung
9.2.2.
Chronisch akute Hepatitis
6.5.
Sonstiges
8.6.
Ödeme und Hämatome
9.2.3.
Cholelithiasis
8.7.
Innere Hernien
9.2.4.
Leberabszess
7.
Pharynx und Oesophagus
8.8.
Darmverlagerung
9.2.5.
Parasitäre Hepatitis
7.1.
Erkrankungen des Pharynx
8.8.1.
Gekröseverdrehung
9.2.6.
Amyloidose der Leber
7.1.1.
Pharyngitis
8.8.2.
Längsachsendrehung
9.2.7.
Lebertumoren
7.1.2.
Fremdkörper im Pharynx
8.8.3.
Blinddarmabknickung
9.2.8.
Sonstiges
7.1.3.
Wunden, Abszesse
8.9.
Darmeinschiebung
7.1.4.
Sonstiges
8.10.
Thrombotisch- Embolische- Kolik
10.
Harnorgane
7.2.
Krankheiten des Oesophagus
8.11.
Innere Verletzungen
10.1.
Harnwegsinfektion
7.2.1.
Wunden
8.11.1.
Darmverletzungen der Stute nach der Geburt
10.2.
Pyelonephritis
7.2.2.
Speiseröhrenfistel
8.11.2.
Mastdarmverletzung
10.3.
Akutes Nierenversagen
7.2.3.
Sonstiges
8.12.
Grasskrankheit
10.4.
Chronisches Nierenversagen
8.13.
chronisch-/rezidivierende Koliken
10.5.
Renale Tubulär Azidose
Harninkontinenz
8.
Magen- Darm- Trakt
8.14.
Viszerale Neuropathie
10.6.
8.1.
Erkrankungen des Magens
8.15.
Ileus
10.7.
Urolithiasis
8.1.1.
Gastritis
8.16.
Erkrankungen der Bauchhöhle
10.8.
Verlagerung der Harnblase
8.1.2.
Magenerweiterung
8.16.1.
Peritonitis
10.9.
Missbildungen der Harnwege
89
10.10.
10.11.
10.12.
Tumoren
Harnblasenruptur
Sonstiges
12.8.2.
12.8.3.
12.8.4.
Tumoren und Missbildungen
Penislähmung
Sonstiges
11.
11.1.
Hernien
Hernia diaphragmatica
13.
13.1.
Fortpflanzungsstörungen beim Hengst
Störungen der Hodenfunktion
11.2.
Hernia umbilicalis
13.2.
11.3.
11.4.
11.5.
Hernia funiculi umbilicalis
Hernia inguinalis incarcerata
Hernia scrotalis interstitialis
13.3.
13.4.
Störungen der Nebenhodenfunktion
Veränderungen der Akzessorischen
Geschlechtsdrüsen
Sonstiges
11.6.
Hernia femoralis
14.
11.7.
11.8.
11.9.
Hernia abdominalis
Hernia perinealis
Sonstiges
12.
12.1.
12.2.
12.2.1.
12.2.2.
12.3.
männliche Geschlechtsorgane
Kryptorchismus
Erkrankungen des Hodens
Aseptische und eitrige Hoden- und
Nebenhodenentzündungen
Hodentumoren
Erkrankungen des Samenstranges
14.1.
14.1.1.
14.1.2.
14.1.3.
14.1.4.
14.1.5.
14.1.5.1.
12.4.
12.5.
Hydrocele
Varikocele
14.1.7.
14.1.8.
12.6.
12.7.
12.7.1.
12.7.2.
12.7.3.
12.7.4.
12.8.
12.8.1.
Hämatocele
Erkrankungen des Skrotums und des Präputiums
Wunden, Phlegmone, Abszesse
Tumoren
Posthitis
Phimose/Paraphimose
Erkrankungen des Penis
Wunden und Entzündungen
14.1.9.
14.2.
Nachgeburtsverhalten
Sonstiges
Erkrankungen des Eileiters
Erkrankungen und funktionelle Störungen der
Ovarien
Zwillingsträchtigkeit
Trächtigkeitsverlust durch embrionalen Fruchttod und
Aborte
Erkrankungen der Milchdrüse
15.
15.1.
15.2.
15.3.
15.4.
Infektionskrankheiten der Geschlechtsorgane
EHV I - IV
Salmonellenabort
Contagiöse Equine Metritis (CEM)
Beschälseuche
14.1.5.2.
14.1.5.3.
14.1.6.
weiblichen Geschlechtsorgane,
Fortpflanzungsstörungen
Morphofunktionelle Veränderungen des
Genitaltraktes
Kongenitale Unfruchtbarkeit
Krankheiten des äußeren Genitale
Erkrankungen im Hymenalbereich
Erkrankungen der Vagina und der cervix uteri
Erkrankungen des Uterus
Endometritiden
90
15.5.
Sonstiges
16.
16.3.
16.4.
16.5.
Endokrine Erkrankungen
Erkrankungen der Hypothalamus- HypophysenNebennierenrinden- Achse
Dysfunktion der Pars intermedia
Equines Cushing Syndrom
Hypothalamus- Hypophysen- NebennierenrindenAchse
Störungen der Nebenschilddrüse und
Kalziumhomöostase
Erkrankungen des endokrinen Pankreas
Sonstiges
17.
17.1.
17.1.1.
17.1.2.
17.1.3.
17.1.4.
17.1.5.
Nervensystems
nicht infektiöse Krankheiten
Gehirnerschütterung
Gehirnquetschung
Dummkoller
Ataxie
Cauda- equina- Syndrom
17.1.6.
17.1.7.
17.2.
Epilepsie
Narkolepsie
Krankheiten der peripheren Nerven
17.2.1.
17.3.
Paralytische Geschehen
Infektionskrankheiten des Zentralnervensystems
17.3.1.
17.3.2.
17.4.
17.5.
17.6.
17.6.1.
17.6.2.
17.6.3.
EHV I und IV
Aujeszkysche Krankheit
Bornaviren- Infektion
Tollwut
Flaviviren
West- Nile- Fieber
Frühsommer- Meningoenzephalitis
Tetanus
16.1.
16.1.1.
16.1.2.
16.2.
17.7.
Sonstiges
19.7.2.
Dikrozölliose
20.1.5.
Sonstiges
19.7.3.
Anoplozephalidose
20.2.
Krankheiten der Bindehaut
18.
Infektionen mit Manifestation im Gefäßsystem
19.7.4.
Bandwurm(finnen)befall
20.2.1.
Bindehautentzündung
18.1.
Virusabort- EHV I und IV
19.7.5.
Diktyokaulose
20.2.2.
Conjunktivitis folicularis
18.2.
Equine Infektiöse Arteritis
19.7.6.
Strongyloidose
20.2.3.
Nickhautvorfall
18.3.
Equine Infektiöse Anämie
19.7.7.
Trichostrongylose
20.3.
Erkrankungen der Tränenorgane
18.4.
Afrikanische Pferdepest
19.7.8.
Paraskariose
20.3.1.
Keratoconjunktivitis sicca
18.5.
Infektion mit Chlamydien
19.7.9.
Oxyuridose
20.3.2.
Tränengangstenose
18.6.
Leptospirose
19.7.10.
Habronematidose
20.3.3.
Sonstige
18.7.
Tuberkulose
19.7.11.
Thelaziose
20.4.
18.8.
Malleus
19.7.12.
Parafilariose
20.4.1.
Krankheiten der Hornhaut
Angeborene /kongenitale Anomalien des Auges
einschl. fehlendes Auge
18.9.
Melioidose
19.7.13.
Onchozerkose
20.4.2.
Hornhautverletzungen
18.10.
Tularämie
19.7.14.
Mischinfektion
20.4.3.
Equine Ulzerative Keratitis
18.11.
Listeriose
19.8.
Räude
20.5.
Erkrankungen der Gefäßhaut
18.12.
Borreliose
19.8.1.
Sarkoptesräude
20.5.1.
Pigmentanomalien
18.13.
Ehrlichiose
19.8.2.
Psoroptesräude
20.5.2.
Uveale Entzündungen
18.14.
Druse
19.8.3.
Choroiptesräude
20.5.3.
Equine rezidivierende Uveitis
18.15.
Botulismus
19.9.
Demodikose
20.5.4.
Blutungen in die Vorderkammer
18.16.
Sonstiges
19.10.
Zeckenbefall
20.6.
Glaukom
19.11.
Läusebefall
20.7.
Krankheiten der Augenlinse
Linsentrübung
19.
Parasitosen
19.12.
Haarlingsbefall
20.7.1.
19.1.
Kokzidiose
19.13.
Gastrophilose
20.7.2.
Linsenverlagerung
19.2.
Kryptosporidiose
19.14.
Rhinoestrus- Befall
20.8.
Krankheiten des Glaskörpers
19.3.
Toxoplasmose
19.15.
Sonstige
20.8.1.
Glaskörpertrübung
19.4.
Sarkozystiose
20.8.2.
Glaskörperblutung
19.5.
Piroplasmose
20.
Auge
20.8.3.
Glaskörperverflüssigung
19.6.
Trypanosomosen
20.1.
Erkrankungen des Augenliedes
20.9.
Erkrankungen des Augenfundus
19.6.1.
Beschälseuche
20.1.1.
Liedödem
20.9.1.
Angeborene Krankheiten des Fundus
19.6.2.
Sonstige
20.1.2.
Liedverletzung
20.9.2.
Entzündungen der Retina und der hinteren Uvea
19.7.
Helminthosen
20.1.3.
Liedentzündung
20.9.3.
Traumatische Myopathie des Nervus opticus
19.7.1.
Fasziolose
20.1.4.
Liedtumoren
20.9.4.
Papillitis
91
20.10.
Krankheiten des Augapfels und der Augenhöhle
24.
Brust- und Lendenwirbelsäule
20.10.1.
Entzündungen der Orbita
24.1.
Frakturen
20.10.2.
Verletzungen in der Augenhöhle
24.2.
20.10.3.
Orbitalphlegmone
24.3.
20.10.4.
Exophtalmus
24.4.
Sonstiges
20.10.5.
20.10.6.
Endophtalmus
Missbildungen und angeborene Defekte des Augapfels
und der Augenhöhle
25.
20.11.
Sonstiges
26.4.8.
Sonstiges
Spondylose
27.
Beckengliedmaße
Tumoren
27.1.
Krankheiten des Oberschenkels
27.1.1.
Wunden
27.1.2.
Myopathien und Parese
Schwanzwirbelsäule
27.1.3.
systemische Muskelkrankheiten
25.1.
Frakturen
27.1.4.
Coxitis akuta
25.2.
Tumoren
27.1.5
HD
25.3.
Sonstiges
27.1.6
Luxatio femoris
21.
Ohr
21.1.
Krankheiten der Ohrmuschel
27.1.7.
OCD der Hüfte/ des Hüftgelenks
21.2.
Krankheiten des äußeren Gehörgangs
26.
Schultergliedmaße
27.1.8.
Frakturen
21.3.
Krankheiten des Mittel- und Innenohres
26.1.
Krankheiten der Schulter
27.1.9.
Tumoren
21.4.
Sonstiges
26.1.1.
Schulterlahmheit
27.1.10.
Sonstiges
26.1.2.
Frakturen
27.2.
Krankheiten am Knie
22.
Schädels
26.1.3.
Sonstiges
27.2.1.
Frakturen
22.1.
Frakturen des Schädels
26.2.
Krankheiten des Oberarmes
27.2.2.
OC, OCD am Knie/ Kniegelenk
22.2.
Osteodystrophia fibrosa
26.2.1.
Frakturen
27.2.3.
Sonstiges
22.3.
Krankheiten der Mandibula
26.2.2.
Tumoren
27.3.
Krankheiten am Unterschenkel
22.4.
Erkrankungen des Atlantookzipitalgelenks
26.2.3.
Sonstiges
27.3.1.
Wunden und Wundinfektionen
22.5.
Sonstiges
26.3.
Krankeiten des Ellenbogens und des Unterarmes
27.3.2.
Frakturen
26.3.1.
Frakturen
27.3.3.
Sehnenruptur im Bereich des Unterschenkels
23.
Halswirbelsäule
26.3.2.
Sonstiges
27.3.4.
Tendinitis
23.1.
Frakturen
26.4.
27.3.5.
Hahnentritt
23.2.
Luxation
26.4.1.
Krankheiten des Karpalgelenkes
Verletzungen der Haut und der Sehnenscheiden am
Karpus
27.3.6.
Sonstiges
23.3.
Tortikollis
26.4.2.
Bursitis praecarpalis
23.4.
Distorsion
26.4.3.
Hygrom
27.4.
Krankheiten am Sprunggelenk
23.5.
Fehlbildungen der HWS
26.4.4.
Tendovaginitis
27.4.1.
Spat
23.6.
Raumfordernde Veränderungen der Wirbelsäule
26.4.5.
Frakturen
27.4.2.
23.7.
Osteomyelitis der Wirbelsäule
26.4.6.
Luxationen
27.4.3.
OC/OCD am Sprunggelenk
Rehbein (Überbein im Bereich des
Sprunggelenkes)
23.8.
Sonstiges
26.4.7.
Sehnenrupturen
27.4.4.
Entzündungen des Sprunggelenkes
92
27.4.5.
Wunden
30.2.
Krongelekserkrankungen
31.21.
Strahlfäule
27.4.6.
30.2.1.
OC/ OCD im Bereich des Krongelenks/ Kronbeins
31.22.
Sonstiges
27.4.7.
Hygrops des Sprunggelenkes
Wunden und Entzündungen der Sehnenscheiden am
Sprunggelenk
30.2.2.
Subluxation des Krongelenks
27.4.8.
Frakturen der Tarsalknochen
30.2.3.
Sonstiges
27.4.9.
Luxation der Tarsalknochen
30.3.
Luxation des Kronbeins
27.4.10.
Sonstiges
30.4.
Kronbeinfraktur
30.5.
Sonstiges
28.
Mittelfuß
28.1.
Wunden
31.
Huf
28.2.
Frakturen
31.1.
Aseptische Huflederhautentzündung
28.3.
Überbein
31.2.
Steingalle
28.4.
Tendinitis
31.3.
Infektiöse Huflederhautentzündung
28.5.
Erkrankungen der Fesselbeugesehnenscheide
31.4.
Hufrehe
28.6.
Sonstiges
31.5.
Nageltritt
31.6.
Hufkrebs
29.
Fesselgelenk und Fessel
31.7.
Hufgelenksentzündung
29.1.
Arthritiden
31.8.
Hufbeinluxation
29.2.
Fesselringbandsyndrom
31.9.
Hufbeinfraktur
29.3.
Luxationen
31.10.
Strahlbeinfraktur
29.4.
Gleichbeinfraktur
31.11.
OC/ OCD im Bereich des Strahlbeines
29.5.
Sesamoidose
31.12.
Erkrankungen der Hufrolle
29.6.
Fesselbeinfraktur
31.12.1.
Hufrollenentzündung
29.7.
OC/OCD im Bereich des Fesselgelenks/ Fesselbeins
31.12.2.
Sonstiges
29.8.
Stelzfuß
31.13.
Erkrankungen des Hufknorpels
29.9.
Bärenfüßigkeit
31.14.
Flach-/ Vollhuf
29.10.
Mauke
31.15.
Zwanghuf
29.11.
Polydaktylie
31.16.
Bockhuf
29.12.
Sonstiges
31.17.
Hornsäule
31.18.
Ringbildung am Huf
30.
Krone, Krongelenk und Kronbein
31.19.
Lose Wand
30.1.
Kronentritt
31.20.
Hohle Wand
93
Anhang A2 Checkliste zu Haltung und Fütterung (nach Beyer, 1998, verändert)
I. Haltung/Betreuung
1. Größe der Liegefläche (m2)
2
a) Einzelbox (min. 16 m )
2
b) Gruppenbox (min. 12m /Pferd)
2. Kontaktaufnahme mit
Nachbarpferden
Trennwandgestaltung (Höhe, Material,
Öffnungen)
Trennwandaufsatz (Gitter, Stangen etc.)
3. Kontakt zur Außenwelt
Anzahl geöffneter Fenster:
Anzahl Pferde mit uneingeschränkter Möglichkeit,
die Außenwelt zu beobachten (> 2/3, ½ der
Pferde etc.)
Frei begehbare Paddocks:
4. Qualität des Einstreumaterials
Struktur, Saugfähigkeit, Schimmelbefall, Menge je
Box ausreichend? gleichmäßig verteilt?
5. Entfernen von Kot- und Nassstellen
Wie oft/Tag?
6. Stalltemperatur
Weicht nur geringfügig von Außentemp. ab?
Werden lediglich Temp.- Extreme abgeschwächt?
7. Maßnahmen zur Staubvermeidung
bei Heuvorlage/beim Fegen
Anzahl/Art der Maßnahmen:
z.B. Anfeuchten des Bodens etc.
8. Lichteinfall/Helligkeit der Stallung
2
2
Fensterfläche m /Grundfläche m ?
Beleuchtungsstärke in lux ?
9. Auslauf im Sommerhalbjahr
täglich?, in Form von Weidehaltung?, Größe der
Weidefläche (mind. 0,5 ha)?
10. Auslauf im Winterhalbjahr
täglich?, Dauer in Std. (mind. 4 Std.)?
Größe und Gestaltung? Kann gallopiert werden?
11. Form der Auslaufgewährung
immer einzeln?, in Gruppen?
12. Gestaltung der Auslaufoberfläche
Auch bei anhaltend nasser Witterung
uneingeschränkt tragfähig? Drainage?
13. Häufigkeit, Dauer und Form der
Auslaufgewährung für güste, tragende
und Stuten mit Fohlen bei Fuß
identisch?
14. Hufpflege/Schmiedetermine
Regelmäßigkeit der Versorgung (alle 8 – 10
Wochen)
94
II. Fütterung
15. Raufutterfressplatz ist so gestaltet,
dass die Pferde mit gesenktem Kopf
im Ausfallschritt fressen können
16. Fütterungsvorrichtung ist geeignet
um Raufutter auf Vorrat vorzulegen
17. Die Raufuttervorlage erfolgt ad
libitum
18. Qualität der Silage/ des Heus
Vielfältigkeit der Artenzusammensetzung
Verunreinigung/ Schimmelpilzbefall etc.
19. Zustand der Futterkrippen ist
hygienisch einwandfrei?
20. Die tägliche Kraftfuttergabe erfolgt
in mindestens drei Einzelrationen
21. Die Kraftfuttergabe erfolgt stets
nach der Raufuttergabe
22. Es erfolgt eine regelmäßige und
individuelle Gabe von Mineralfutter
23. Bei Gruppenhaltung ist
mindestens ein Fressplatz pro Tier
vorhanden
24. Die Tränken sind möglichst weit
von den Krippen entfernt angebracht
25. Die Tränken sind hinsichtlich der
Hygiene in einem einwandfreien
Zustand
95
GENERAL DISCUSSION
Pedigree and fertility data sets of Holstein Warmblood horses were analysed to
determine parameters of population structure as well as the influence of inbreeding
on fertility measures and on the occurrence of stillbirth. In course of the study, some
problems could be addressed concerning the recording of fertility and reproductive
health data. Inconsistent and incomplete phenotypes are capable of affecting and
skewing statistical analysis (Day et al., 1995; Mucha et al., 2012). Therefore, in
addition to the findings on genetic diversity and their impacts on female reproductive
performance, a model-like database for veterinary field data was initiated to generate
the epidemiological knowledge needed to provide reasonable emphases for selection
with regard to health aspects in the future.
Genetic diversity in the Holstein Horse breed
The results on population structure illustrate the occurrence of the loss of genetic
diversity within the Holstein horse breed related to unequal founder contributions
caused by the intensive use of particular sires or sire lines. Mean inbreeding
coefficients were estimated at a moderate level and most of the inbreeding was found
to have evolved in five recent generations. Based on the statements of Nomura et al.
(2001) and Sierszchulski et al. (2005) that an intensive use of preferred males could
also cause increasing changes in inbreeding coefficients, today’s average inbreeding
should not be increased significantly. With a mean value of 55.3 effective animals,
the effective population size (Ne) was still estimated at a low level. This might be
attributed to the breeding policies in the more distant decades, with closed studbooks
and a restricted licensing of foreign stallions. A closer look at the recent past showed
an increase in the number of effective animals (Ne) in conjunction with a stagnating
96
tendency in the rate of inbreeding (∆F). This might be effected by some changes in
breeding policies, especially against the background of foreign stallions’ access to
the breeding programme. However, the critical size for Ne, i.e. the size below which
the fitness of a population steadily decreases, lies between 50 and 100 animals
(Meuwissen and Woolliams, 1994). According to this, the effective number of animals
in the Holstein horse breed needs to be increased as a long-term objective in order to
preserve a necessary volume of genetic variability. It is necessary to presume a
reduction concerning the increase in inbreeding per time (Meuwissen and Woolliams,
1994). The stagnating tendency for the increase in inbreeding already described for
the Holstein horse breed suggests that this presumption is to be met in future.
Therefore, optimum contribution selection (Meuwissen, 1997) might be considered as
a possible approach to maximize genetic gain using predefined values of increases
in inbreeding. In this regard, it is to be accepted that breeders’ decision-making is
restricted by intervention of the breeding association.
Effect of inbreeding on female fertility in the Holstein horse breed
According to our results, increased inbreeding does not lower female fertility traits
such as the individual mating outcome or the outcome of the season’s first mating for
this breed whether they are modelled as a trait of the mare or as a trait of the
expected foal. Treating them as traits of the mare, the individual outcome of a mating
as well as the outcome of the season’s first mating were influenced significantly
positively (p ≤ 0.05). In Livestock species, positive inbreeding effects on fertility are
rare (Köck et al., 2009). In Austrian Landrace pigs a positive effect of sire inbreeding
on the number of piglets born in total and the number of piglets born alive was found
by Köck et al. (2009). As a reason, they suspected better sperm quality in the inbred
sires. This was partly confirmed by Boer (2007), detecting significantly higher
97
ejaculate volume in Frisian stallions with an increase in average inbreeding.
Reversely, Van Eldik et al. (2006) found that a certain level of inbreeding also affects
aspects of sperm production and quality in Shetland pony stallions. In particular,
coefficients of inbreeding above 2% were associated with lower percentages of
motile (p ≤ 0.01) and morphologically normal sperm (p ≤ 0.001) (Van Eldik et al.,
2006). These ambiguous findings could give cause for some further investigations on
the impact of sire inbreeding on female reproductive performance and on possible
inbreeding effects on sperm quality parameters in the Holstein horse breed.
Confirming this need for further research on the effects of the sire on female
reproductive efficiency, the stallion was detected to explain the greater part of total
variance for the foaling rate and the outcome of season’s first mating, in the current
study.
Despite the low number of recorded phenotypes (n = 1,237), the occurrence of
stillbirth was affected significantly by increased foal inbreeding. An Increased
inbreeding coefficient of the progeny equally increased the risk of stillbirth. Previous
studies on stillbirth in Holstein dairy cattle (Hinrichs et al., 2011) and on retained
placenta in Frisian horses (Sevinga et al., 2004) showed similar results. In both
cases, increased inbreeding of the expected offspring had a significantly negative
impact on the frequency of the studied fertility disorder, whereas the inbreeding
coefficient of the dam did not have any impact (Sevinga et al., 2004; Hinrichs et al.,
2011). Higher embryonic mortality in cattle with increased embryonic inbreeding was
already reported by Van Raden and Miller (2006). Therefore Hinrichs et al. (2011)
stated that it is not surprising when increased inbreeding also results in an increased
risk of stillbirth if inbreeding has negative effects on the survival of the embryo. A
similar situation in horses is quite conceivable, but further corresponding studies are
lacking.
98
The values of heritability for all of the studied traits are calculated at a low level
(h2 ≤ 0.1), with a declining trend for the frequency of stillbirth if it is modelled as a trait
of the expected foal. Such low values of heritability for fitness-associated traits are in
accordance with common literature on horses and cattle, respectively (e.g. Van
Raden et al., 2004; Sairanen et al., 2009; Hinrichs et al., 2011; Mucha et al., 2012).
The findings motivate further investigations especially on the impact of increased
inbreeding on the frequency of some additional fertility disorders (e.g. early abortion
and twinning) in Holstein horses. However, for this kind of research it is essential to
work with the largest possible number of high quality phenotypes. As discussed by
Mucha et al. (2012) in their studies on twinning and fertility in Thoroughbred horses,
reliability of the estimated parameters strongly depends on the completeness of
dataset as well as on precise record-keeping. A crucial factor in this chain is the
onsite diagnostics of mares and the precise work of veterinarians (Day et al., 1995).
Therefore, it is advisable to improve the recording of overall health and fertility as well
as fertility disorders not only in Holstein horses.
Consistent recording of health data in horse breeding
The introduction of new selection strategies (genomic selection) as well as the
already mentioned problems in quality and quantity of phenotypes analysing genetic
and non-genetic effects on fertility and health aspects required adjustments to
breeding schemes and data recording (Day et al., 1995; Mucha et al., 2012;
Sarnowski et al.., 2013).
In most of the breeding associations, the mandatory part of a foaling report sent in by
the breeder regards information of a general nature (e.g. date of foaling, place of
foaling, parents, markings and sex of the foal). Further important questions
concerning health, fertility and fertility disorders are requested but not obliged to be
99
answered (see also: Dohms, 2002). These foaling or mating reports are often used
as a primary source of fertility information (Dohms, 2002). Against this background, it
was possible to explain the low number of observations for twinning (n = 96) and
stillbirth (n = 1,237) within the studied dataset. Furthermore, it became apparent that
there is a need for a more consistent and comprising data recording.
To minimize the number of unreported cases, breeding associations need to
overcome this problem creating incentives for the breeders to give complete
information.
Further indications concerning insufficient data stock were found in a field study to
assess veterinary data on Holstein Warmblood horses. The current data situation
was checked as well as the fundamental feasibility of health monitoring. Merely 50%
of the involved veterinarians provided data of their served broodmare stock. The fact
that only a part of the involved equine facilities (breeders and veterinarians) send in
their data bears evidence for scepticism towards the corresponding exchange of
information. Since the consent of stakeholders concerning communication of their
data is imperatively required in a future project, all involved institutions are called to
do extensive explanatory work (Hartig et al., 2013). In course of database
development, clearly defined access and usage rights are important prerequisites
(Egenvall et al., 2011; Hartig et al., 2013).
The recordings of veterinarians in the current study were characterised by
inconsistent use of symbols and abbreviations and mostly handwritten. A direct
relation between one record and a single broodmare (by Unique Equine Live
Number, UELN) was given for a minority of animals. However, logically linked data is
indispensable. A subsequent categorisation of recordings needs to be allowed by a
specially developed key system (Appendix A1, Chapter Four) to achieve
epidemiological evaluation regarding incidence and prevalence of special diseases
100
(Egenvall et al., 2011). Sustainable and efficient use of veterinary data requires
breeding organisations to establish consistent monitoring systems as well as secure
and centrally controlled data transfer solutions. The future challenge will be to
allocate existing resources of veterinary data processing (e.g. working with highly
compatible interfaces) to limit extra time and financial effort for all involved
stakeholders.
References
Boer, M. 2007. Effects of inbreeding on semen quality of Friesian stallions.Major
thesis Animal Breeding and Genetics (ABG-8043), Animal Breeding and
Genomics Centre, Wageningen University.
Day, J. D., L. D. Weaver, and C. E. Franti. 1995. Twin pregnancy diagnosis in
Holstein cows: discriminatory powers and accuracy of diagnosis by transrectal
palpation and outcome of twin pregnancies. Can. Vet. J. 36(2):93–97.
Warendorf.
Egenvall, A., A. Nødtvedt, L. Roepstorff, and B. Bonnett. 2011. Integrating databases
for research on health and performance in small animals and horses in the Nordic
countries. Acta Vet. Scand. 53 Suppl 1:S4. doi:10.1186/1751-0147-53-S1-S4.
Hartig, W., H. Houe, and P. H. Andersen. 2013. Monitoring of equine health in
Denmark: a survey of the attitudes and concerns of potential database
participants. Prev. Vet. Med. 109(1-2):83–91.
doi:10.1016/j.prevetmed.2012.06.004.
101
Hinrichs, D., and G. Thaller. 2011. Pedigree analysis and inbreeding effects on
calving traits in large dairy herds in Germany. J. Dairy Sci. 94(9):4726–4733.
doi:10.3168/jds.2010-4100.
Köck, A., Fürst-Waltl, B. and Baumung, R. 2009. Effects of inbreeding on number of
piglets born total, born alive and weaned in Austrain Large White and Landrace
pigs. Archiv für Tierzucht 52(1):51–64.
Meuwissen, T. H. 1997. Maximizing the response of selection with a predefined rate
of inbreeding. J. Anim. Sci. 75(4):934–940.
Meuwissen, T. H., and J. A. Woolliams. 1994. Effective sizes of livestock populations
to prevent a decline in fitness. Theor. Appl. Genet. 89(7-8):1019–1026.
doi:10.1007/BF00224533.
doi:10.1017/S1751731109990553.
Sarnowski, S., and Stock, K. F. and Kalm, E. 2013.Standardisierte Erfassung von
Gesundheitsdaten beim Pferd. Vortragstagung der DGfZ und GfT am 4./5.
September 2013 in Göttingen; A23.
Anim. Sci. 82(4):982–986.
102
Van Eldik P., E.H. van der Waaij, B. Ducro, A.W. Kooper, T.A.E. Stout, and B.
Colenbrander. 2006. Possible negative effects of inbreeding on semen quality in
Shetland pony stallions. Theriogenology 65(6):1159–1170.
doi:10.1016/j.theriogenology.2005.08.001.
Van Raden P. M. and R. H. Miller. 2006. Effects of Nonadditive Genetic Interactions,
Inbreeding, and Recessive Defects on Embryo and Fetal Loss by Seventy Days.
Van Raden, P. M., A. H. Sanders, M. E. Tooker, R. H. Miller, H. D. Norman, M. T.
Kuhn, and G. R. Wiggans. 2004. Development of a National Genetic Evaluation
for Cow Fertility. Journal of Dairy Science 87(7):2285–2292.
doi:10.3168/jds.S0022-0302(04)70049-1.
103
GENERAL SUMMARY
In horse-breeding programs working under the conditions of pure breeding with
closed studbooks and restricted licensing of foreign stallions, closely related
individuals are expected. An increase in average inbreeding bares the risk of
negative impacts on low heritable, fitness-associated traits such as fertility and
health. Simultaneously, these traits are the key factors in economic horse breeding
with central importance for animal welfare. In many cases, functional traits are
anchored in the breeding goal of a horse breeding association, but their recording is
still performed indirectly by auxiliary traits. However, the investigation of genetic and
non-genetic impact factors on health and fertility as well as the application of new
selection strategies (genomic selection) requires standardised and comprehensive
phenotyping. The aim of the present study was to investigate the impacts of
population structure on female reproductive performance, using the example of the
Holstein horse breed. Additionally, shortcomings in the availability, recording and
standardisation of health data were to be addressed and possible solutions should be
elaborated.
Chapter One represents a general overview of the occurrence of inbreeding
depression for various traits in horse breeding. Literature research indicated no
overall trend concerning the susceptibility of horse populations to the occurrence of
inbreeding depression. The quality and quantity of pedigree data, phenotypes and
sample sizes fluctuated between particular studies and the stated conclusions were
found to be inconsistent.
The aim of Chapter Two was to demonstrate the population structure of the Holstein
horse breed using pedigree data, focusing on the average inbreeding coefficient (F),
the rate of inbreeding over time (ΔF) and the effective population size (Ne).
104
Additionally, proportions of foreign blood and the contributions of outstanding
founders were estimated. Unbalanced contributions of founders and concentration
processes on certain sire lines were shown in the presence of moderate inbreeding
and low effective population size (Ne = 55). The findings suggest the loss of genetic
diversity and indicate the need to increase the number of effective animals in order to
preserve a necessary volume of genetic variability.
Chapter Three investigated the possible impacts of population structure on female
reproductive performance (individual foaling rate) and on the occurrence of fertility
disorders (stillbirth) in Holstein Warmblood mares. If the inbreeding coefficient of the
mare was considered in the statistical model, no negative effect of inbreeding on the
observed traits was found. Modelling the inbreeding coefficient of the expected
offspring, a significantly negative impact on the occurrence of stillbirth was detected
(b = 6.77, p ≤ 0.001). The low number of recorded stillbirths in the dataset (n = 1,237)
suggested a higher amount of unreported cases. This fact indicates weaknesses in
data recording.
A field study on recording and standardisation of veterinary data was described in
Chapter Four. Its aim was to develop a comprehensive, model-like phenotyping for
veterinary findings on horses. Inadequate data returning showed scepticism towards
a corresponding exchange of information. Veterinary findings were recorded
inconsistently and mostly handwritten. A direct relation between one record and a
single broodmare was given for a minority of animals. Epidemiological evaluation of
the data regarding the prevalence of special diseases was impossible. A subsequent
categorisation of recordings by a specially developed key system(Appendix A1,
Chapter Four) was impractical. If veterinary data is to be utilised for breeding and
consulting purposes in the future, improvements are required. Developing a
105
correspondent database, a consistent key system, maximum data security and
predefined rules of data access and usage should be ensured.
106
ZUSAMMENFASSUNG
In Zuchtpferdepopulationen unter Reinzuchtbedingungen ist bei geschlossenem
Stutbuch und eingeschränkter Zulassung fremdblütiger Hengste mit erhöhter
Verwandtschaft der zu verpaarenden Tiere zu rechnen. Steigende Inzucht birgt
erhöhte Risiken negativer Ausprägungen gering erblicher, Fitness assoziierter
Merkmale wie Fruchtbarkeit und Gesundheit. Gleichzeitig sind diese Merkmale die
Schlüsselfaktoren wirtschaftlicher Pferdezucht und haben auch im Sinne des
Tierschutzes eine zentrale Bedeutung. Vielfach sind funktionelle Merkmale im
Zuchtziel
der
Pferdezuchtprogramme
verankert,
werden
jedoch
nur
über
Hilfsmerkmale erfasst. Die Untersuchung genetischer und nicht genetischer Faktoren
auf Gesundheit und Fruchtbarkeit sowie die Einführung neuer Selektionsstrategien
(genomische Selektion) machen jedoch eine standardisierte, flächendeckende
Erfassung entsprechender Phänotypen notwendig. Ziel dieser Arbeit war es, am
Beispiel des Holsteiner Pferdes, die Auswirkungen der Populationsstruktur auf die
weibliche Fruchtbarkeit zu untersuchen. Auch sollten mögliche Schwächen in Bezug
auf Verfügbarkeit, Erfassung und Standardisierung von Gesundheitsdaten sowie
mögliche Lösungsansätzen aufgezeigt werden.
Kapitel Eins gibt einen allgemeinen Überblick zu Erkenntnissen bezüglich des
Auftretens von Inzuchtdepression auf unterschiedliche Merkmalskomplexe der
Pferdezucht. Die Literaturrecherche zeigte keinen allgemeinen Trend bezüglich der
Anfälligkeit von Pferdepopulationen für das Auftreten von Inzuchtdepression. Die
Qualität und Quantität der verwendeten Pedigree Daten, Phänotypen und
Stichprobenumfänge variierte zwischen den Studien. Die Ergebnisse stellten sich
uneinheitlich dar.
107
Zielsetzung in Kapitel Zwei war die Darstellung der aktuellen Populationsstruktur des
Holsteiner Pferdes auf Grundlage von Pedigree Daten.
Im Vordergrund der Untersuchung standen der durchschnittliche Inzuchtkoeffizient
(F) und der mittlere Inzuchtanstieg je Zeiteinheit (ΔF) sowie die effektive
Populationsgröße (Ne). Zusätzlich sollten Fremdblutanteile und genetische Beiträge
einflussreicher Gründertiere berechnet werden. Bei moderater Inzucht und niedriger
effektiver Populationsgröße (Ne = 55) zeigten sich ungleichmäßige Genanteile
einzelner Linienbegründer mit Konzentrationsprozessen auf einzelne Hengstlinien.
Dies lässt den Verlust an genetischer Diversität vermuten und verdeutlicht die
Notwendigkeit einer Steigerung der effektiven Populationsgröße, um auch zukünftig
ein gesichertes Maß an genetischer Variabilität zu erhalten.
Kapitel Drei der Studie hatte zum Ziel, mögliche Einflüsse der Populationsstruktur auf
die weibliche Fruchtbarkeitsleistung (individuelle Abfohlrate) sowie auf das Auftreten
von Fruchtbarkeitsstörungen (Totgeburten) bei Holsteiner Stuten darzustellen. Unter
Berücksichtigung des durchschnittlichen Inzuchtkoeffizienten der Stute zeigte sich
kein negativer Einfluss der Inzucht auf die beobachteten Merkmale. Wurde der
Inzuchtkoeffizient des zu erwartenden Nachkommen in die Auswertung integriert,
zeigte sich ein signifikant negativer Einfluss bezüglich des Auftretens von
Totgeburten (b = 6,77, p ≤ 0,001). Die geringe Anzahl dokumentierter Totgeburten (n
= 1.237) im Gesamtdatensatz lässt eine hohe Zahl nicht dokumentierter Fälle
vermuten und deutet auf Schwächen in der Merkmalserfassung hin.
Kapitel Vier beschreibt einen Feldversuch zur Erfassung und Standardisierung von
veterinärmedizinischen
Entwicklung
und
Daten
Erprobung
mittels
einer
Datenbank.
Ziel
flächendeckenden
war
die
modellhafte
Phänotypisierung
von
Diagnosen und Befunden aus der Pferdemedizin. Ein unzureichender Datenrücklauf
seitens der Züchter und Veterinäre verdeutlicht eine gewisse Skepsis bezüglich des
108
Informationsaustausches. Die Diagnosedaten wurden uneinheitlich und meist
handschriftlich erfasst. Ein klarer Einzeltierbezug war nur bei einer Minderheit der
Diagnosen gegeben. Epidemiologische Betrachtungen zur Identifikation von
Krankheitsschwerpunkten waren nicht möglich.
Eine
Kategorisierung
der
Diagnosen
mittels
eines
eigens
entwickelten
Schlüsselsystems (Anhang A1, Kapitel Vier) konnte nicht durchgeführt werden.
Sollen veterinärmedizinische Daten zukünftig für Zuchtarbeit und Beratung nutzbar
gemacht werden, besteht Handlungsbedarf. Bei der Erarbeitung entsprechender
Systeme sind neben einem einheitlichen Diagnoseschlüssel und größtmöglicher
Datensicherheit, klar definierte Zugriffs- und Nutzungsrechte zu beachten.
109
110
DANKSAGUNG
An dieser Stelle möchte ich all denen danken, die zum Gelingen dieser Arbeit
beigetragen haben.
Mein besonderer Dank gilt meinem Doktorvater Herrn Prof. Dr. Joachim Krieter für
die Überlassung des Themas, die wissenschaftliche Betreuung und die gewährten
Freiräume bei der Anfertigung dieser Dissertation. Ebenfalls bedanke ich mich für die
Möglichkeit, meine Ergebnisse auf Tagungen im In- und Ausland zu präsentieren.
Herrn Professor Georg Thaller danke ich für die Übernahme des Koreferates.
Die finanzielle Förderung dieser Arbeit erfolgte dankenswerter Weise durch die H.
Wilhelm Schaumann Stiftung, Hamburg. Besonderer Dank gebührt an dieser Stelle
Herrn Prof. Dr. Dr. h.c. mult. Ernst Kalm für die umfangreiche Unterstützung bei der
Planung und Umsetzung des Projektes.
Für die uneingeschränkte Kooperation in allen Fragen der Datenbereitstellung und
für die umfassende Unterstützung im Zuge der eigenen Datenerfassung möchte ich
mich bei allen Mitarbeitern der Geschäftsstelle des Holsteiner Verbandes, Abteilung
Zucht in Kiel bedanken.
Herrn Dr. Thomas Nissen sowie Herrn Götz Hartmann und Frau Dr. Stefanie
Bergmann sei besonders herzlich für die intensive fachliche Beratung und die vielen
wertvollen Gespräche gedankt.
Allen beteiligten Holsteiner Pferdezüchtern und Tierärzten danke ich für die
vertrauensvolle Zusammenarbeit und die vielen Einblicke in Ihre tägliche Arbeit.
Stellvertretend seien hier Hans Joachim Ahsbahs (Bokel), Familie Magens
(Ottenbüttel), Familie Horns (Bredenbekshorst), Michaela Kölling (Dägeling) und Herr
Dr. Achilles (Bad Segeberg) genannt.
Ein ganz besonders großes Dankeschön gilt Dr. Claas Heuer, Dr. Dirk Hinrichs, Dr.
Jens Tetens, Dr. Nina Krattenmacher und Dr. Anita Ehret für Ihre unermüdliche,
geduldige und humorvolle Unterstützung in allen wissenschaftlichen und statistischen
Fragen.
Weiterhin möchte ich mich bei allen Kollegen für die unvergessliche Zeit am Institut
und die vielen ausgelassenen Stunden nach Feierabend bedanken. Besonderer
Dank gilt Claas mit Kerrin und Antje, Marvin und Hannah, Anita und Achim sowie
Irena, Danica, Bettina, Anna-Lena, Katharina und Kathrin für Ihre großartige
Unterstützung in allen Lebenslagen weit über die Institutsgrenzen hinaus.
Nicht zuletzt gilt mein größter Dank meinen Eltern und meiner Familie samt allen
Freunden und Weggefährten. Ihre uneingeschränkte Unterstützung und das große
Vertrauen haben entscheidend zum Gelingen dieser Arbeit beigetragen.
111
112
LEBENSLAUF
Name:
Geburtsdatum:
Geburtsort:
Familienstand:
Staatsangehörigkeit:
Lukas Philipp Roos
20.08.1981
Speyer/Rhein
ledig
Deutsch
Schulische Ausbildung
1994 – 2001
Gymnasium der Nikolaus - von - Weis Schulen, Speyer
Abschluss: Allgemeine Hochschulreife
Berufsausbildung
2001 – 2004
Ausbildung zum staatlich anerkannten Tierarzthelfer
Tierarztpraxis Dr. Wilhelm Drewes, Fachtierarzt für Pferde
in Strausberg
Studium
2004 – 2007
B. Sc. Studium der Agrarwissenschaften an der Humboldt
Universität zu Berlin, Fachrichtung Nutztierwissenschaften
Abschluss: Bachelor of Science
2007 – 2010
M. Sc. Studium der Agrarwissenschaften an der ChristianAlbrechts- Universität zu Kiel, Fachrichtung
Nutztierwissenschaften
Abschluss: Master of Science
Praktika
2005
Landwirtschaftliches Unternehmen und Beratung Peter
Munzinger, Reichenberg
2006
Biolandhof Wendt, Berlin
Berufliche Tätigkeit
Januar – April 2009
Studentische Hilfskraft in der Geschäftsstelle des
Holsteiner Verbandes, Abteilung Zucht, Kiel sowie
Stutenleistungsprüfung (Station), Lürschau
August – Dezember 2010 Milcherzeugerberatung des LKV Brandenburg,
Waldsieversdorf
Seit Mai 2011
Wissenschaftlicher Mitarbeiter am Institut für Tierzucht
und Tierhaltung der Christian- Albrechts- Universität zu
Kiel bei Prof. Dr. J. Krieter
113

Reproduction and health in Holstein Warmblood mares

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