in Crested Ducks (Anas platyrhynchos f. d.)

Arch.Geflügelk., 74 (3). S. 203–209, 2010, ISSN 0003-9098. © Verlag Eugen Ulmer, Stuttgart
Brain alterations, their impact on behavior and breeding strategy
in Crested Ducks (Anas platyrhynchos f. d.)
Hirnveränderungen, ihr Einfluss auf das Verhalten und Zuchtmanagement bei
haubentragenden Hausenten (Anas platyrhynchos f. d.)
Julia Mehlhorn and G. Rehkämper
PhD Award 2009 of German Branch of WPSA
Introduction
Domestication could be seen as a selective process associated with a lot of alterations and greater variability in a
lot of signs in domestic animals if compared to their wild
ancestors (PRICE, 1999). During the course of domestication a lot of breeds have been developed which show alterations in e.g. body size, coloring, habitat or behavior. Also
alterations can be found in brain size and brain composition (KRUSKA, 1980; EBINGER, 1995), not only in comparison to wild animals but also between different breeds
(REHKÄMPER et al., 2003, 2008). One example for this is the
Crested Duck (CR hereafter, Figure 1), which is characterized by a feather crest.
The existence of a crest can be associated with changes
in skull and brain morphology. In crested chickens the
frontal bones form a protuberance, into which the telencephalon is displaced and show peculiarities in size and
composition (FRAHM and REHKÄMPER, 1998). In contrast,
the crest in CR is located in the parietal part of the skull
underlain by a cushion of fat and connective tissue. Additionally, many CR bear a fat body inside the skull that
could vary in size and position (Figure 2). Depending on
its size and position in relation to the brain, a negative
effect on brain function cannot not be excluded and in fact,
often coordination of locomotion is poor as demonstrated
by a tottering walk, and some animals are even unable to
right themselves up after fallen on their back (BRINKMEIER,
1999; BARTELS and KUMMERFELD, 2001; BARTELS et al., 2001;
FRAHM et al., 2001; CNOTKA et al., 2006, 2007, 2008).
Hereditary aspects and high pre- and postnatal mortalities
were discussed by BARTELS and KUMMERFELD (2001) and
BARTELS et al. (2001).
The German government has asked experts to work out
some guidelines for the breeding of fancy poultry (“Gutachten zur Auslegung von § 11b des Tierschutzgesetzes
[Verbot von Qualzüchtungen]”). These guidelines discuss
crested ducks critically and propose to consider prohibiting
the breeding of CR with regards to the German law preventing cruelty against animals.
In this study an analysis of the observed problems, their
possible origin and of the brains of CR was done. Additionally a behavioral test and a breeding strategy had to be
developed that would allow a breeder to discover animals
Working Group Behavior and Brain, C.&O. Vogt Institute of Brain Research,
University of Düsseldorf, Germany
Arch.Geflügelk. 3/2010
with large fat bodies even if the undesirable defect is not
obvious and behavior in daily life looks quite normal. The
goal is to eliminate detrimental traits from their breeding
populations, assuming that the condition is heritable
(LANCASTER, 1990). It is proven that the existence of a crest
and its size is not a reliable predictor of the fat body or
behavioral deficits (KRAUTWALD, 1910; BRINKMEIER, 1999;
BARTELS and KUMMERFELD, 2001; FRAHM et al., 2001, 2005)
and thus, other phenotypic measures must be identified
that are associated with this trait. A good breeding management should solve the existing problems rather than
eliminating this old and traditional breed completely.
The present paper draws attention to a behavioral test
that indicates deficits in coordination of locomotion. To
prove the appropriateness of this test, individuals preselected by the test were used in a special breeding program.
Number of offspring, coordination of locomotion and morphology of skull and brain were recorded. In parallel the
brain size and brain composition was analyzed in detail in
this breed and it was checked whether individuals identified as malfunctional have a more or less prominent fat
body inside their skulls.
Material and Methods
Behavioral test
In total, 26 adult CR (11 drakes, 15 ducks) from our own
stock were used for behavioral test and brain analysis. The
behavioral test should check the motor abilities and should
challenge the system of motor coordination of CR. The
idea for the used ‘righting test’ test was based on the fact
that ducks with serious problems in locomotion coordination often fall down on their back and then are unable to
right themselves and stand up. Among the 26 ducks investigated, ten individuals showed motor incoordination such
as staggering during moving or tumbling down at least one
time in their lives. These ducks exhibited the symptoms in
different manners but appeared quite normal in their daily
lives. The deficits became apparent during stressful situations like collecting or handling of the ducks. After such
treatment, many of them recovered quickly and any deficits were inconspicuous again in daily life. The other 16
ducks had no detectable deficits in motor coordination and
were completely inconspicuous in their locomotion behavior. So, the following ‘righting test’ was employed on two
distinguishable groups of ducks, “affected” CR (n = 10)
and “normal” CR (n = 16). For the test, all CR were placed
on their backs and the required time needed to stand up on
204
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
Figure 1. Portrait of a Crested Duck (CR)
Kopfstudie einer Landente mit Haube
Figure 2. Dorsal view of a Crested Duck brain with incorporated
middle sized fat body (*)
Landentengehirn mit einem Fettkörper mittlerer Größe (*), von
dorsal gesehen
both feet was recorded. This procedure was repeated 13
times per animal over a period of three months. The average time was calculated for each individual. Differences
between the 2 examined groups for average righting time
was calculated and evaluated using the Mann-Whitney
Rank Sum Test.
body sizes to correct for the influence of body size. This
method involves the calculation of a regression line slope
that expresses the brain (or brain component or fat body)
size/body size relationship. To test for differences in brain
structure volumes between CR and pooled reference
breeds allometric size indices [(brain component size/expected brain component size) * 100] were calculated. The
indices represented the distance of individual data points
from the regression line. The expected brain (or brain component size) is the value on the regression line that corresponds to a given individual body weight. A detailed description of these methods for preparation, measurement
and calculation is given in literature (STEPHAN et al., 1988;
FRAHM and REHKÄMPER, 1998; MPOTSARIS and REHKÄMPER,
2006; CNOTKA et al., 2007).
Differences between the 2 examined groups for fat body
volume were calculated and evaluated using the MannWhitney Rank Sum Test. Differences between the size
indices of CR and the reference group were evaluated
using Student’s t-Test. Additionally correlation analyses
between fat body volume and brain size or brain component size were calculated using Pearson product moment
correlation.
Brain analysis
The investigation of the brain anatomy was based on 26 CR
brains from the tested animals. For comparison 26 brains
from three other domestic duck breeds, called Pommeranian Ducks (Po, n = 10, 5 drakes/5 ducks), Abacot Ranger
Ducks (Ar, n = 6, 3 drakes/3 ducks) and “Hochbrutflugenten” (Hb, n = 10, 5 drakes/5 ducks) were used. These
breeds represent the body size variability in domestic
ducks which will be important for brain analyses with allometric methods. All these breeds were uncrested and do
not show, as far as known, any peculiarities like those
observed in CR. All specimens of ducks were obtained from
organized breeders and were at least one year old.
The animals were euthanized with an overdose of pent
barbiturate. After cardiac arrest was confirmed ducks were
perfused with physiological saline solution to wash out the
blood, followed by Bodian’s fluid to fixate the brain. After
this, the brains were carefully dissected, sectioned and
stained for cell bodies. Body weight, total brain volume,
volume of the fat body and the volume of 14 other areas of
the brain (hyperpallium apicale, hyperpallium densocellulare, mesopallium, nidopallium, striatopallidal complex,
septum, hippocampus, area prepiriformis, bulbus olfactorius, tegmentum, cerebellum, tectum, tractus opticus,
diencephalon) were determined. For volume measurements
the contours of brain structures were drawn using a digital
pen and a camera lucida. For calculation of the fresh
volume, the resulting values were multiplied by the section
thickness, the distance between the sections and the
individual conversion factor of shrinkage (volume fresh
brain/sum of serial section volumes). Net brain volume
was calculated as the sum of the single brain components.
In contrast to total brain volume, the net brain volume
does not include the volume of leptomeninges, ventricles,
choroids plexus and remains of brain nerves.
Allometric methods were used for comparison of volumes of brain structures in different breeds with different
Breeding
In total, three years of breeding have been completed. In
the first year three breeding couples were chosen from our
own stock without any special selection. In the following
two years the breeding couples (five in the 2nd year and
three in the 3rd year) were preselected by the ‘righting test’.
Only individuals with the shortest average righting times
were chosen for breeding. All breeding couples were
housed in a separate aviary with their own swimming facility. The eggs were collected every day and hatched by a
common incubator. The ducklings were reared all together
in a separate aviary with good observation conditions.
Eggs that did not hatch were opened three days after the
end of hatching time and the habitus and skull of extant
embryos were investigated. Thus, fertilization rate, hatching rate, number of unhatched ducklings with skull malformations (e.g. perforations of the skull) and number of
(hatched) ducklings with behavioral deficits of these
breeding couples were investigated. Hatched ducks were
checked for skull deformations after growing up as well.
Arch.Geflügelk. 3/2010
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
Differences in the investigated parameters between the
three breeding years were calculated using Chi2-Test.
All research was performed in accordance with the official German regulations for research on animals.
Results
Behavioral test
The ‘righting test’ was employed on two distinguishable
groups of ducks (see above): the 10 individuals with several
observed deficits in coordination of locomotion and the 16
individuals without any behavioral deficits. In contrast to
the “normal” ducks, the “affected” CR performed poorly.
On average they required 13.4 s ± 6.93 with a range from
1.0 to 62.6 s for the ‘righting test’. The “normal” CR
required 1.4 s ± 0.20 s and ranged from 0.5 to 2.9 s. The
average times of the two groups differed significantly
(t = 2.21; DF = 24; p = 0.037).
Brain analysis
On average the body weight of all affected CR investigated
amounted to 2,301 g ± 58.4 and ranged from 1,725 to
2,960 g. The corresponding data on brain size are 6,855
mm3 ± 209 with a range from 5,111 mm3 to 9,547 mm3.
Normal CR ducks show an average body weight of 2,300 g
± 81.7 (range from 1,825 to 2,960 g) and an average brain
size of 6,659 mm3 ± 225 (range from 5,111 to 8,060 mm3).
Two (normal) CR ducks from the examined duck population did not show a fat body. The volumes of the fat bodies
of the other 24 CR ducks varied from 19 mm3 to 3,891 mm3
and from 0.3% to 41% of total brain volume, respectively.
The fat body size of the two groups (consisting of 10
“affected” and 16 “normal” ducks) differed significantly.
Ducks with deficits in coordination of locomotion showed
a significantly larger fat body (1,512 mm3 ± 371) than
ducks without such problems (637 mm3 ± 138; 2-tailed
t-test, t = 2.583, DF = 24, p = 0.016). Most frequently mid-
205
dle-sized fat bodies were positioned in the tentorium cerebelli (Figure 2). Additionally, the fat bodies often extended
to rostral between the two hemispheres (Figure 3). There
was no significant correlation between the fat body size
and the latency to right (r = 0.278, p = 0.169).
The allometric comparison of the brain and brain structure volume in relationship to the body weight of all ducks
is represented in Table 1. CR individuals (n = 26) exhibit a
significantly larger total brain volume in comparison to the
pooled reference ducks (n = 26, t = 2.651, DF = 50, p = 0.011).
The total brain volume included, if present, the volume of
the fat body. But, as can be seen in Table 1 and Figure 4,
net brain volume of CR was significantly smaller in an
allometric comparison to the reference breeds (t = –2.325,
DF = 50, p = 0.024). Among the 14 brain structures delineated, in CR 10 were not reduced compared to reference
breeds. A relative reduction of cerebellum, tegmentum,
apical hyperpallium and olfactory bulb was observed in
comparison to the reference group (cerebellum: t = –2.882,
DF = 50, p = 0.006; tegmentum: t = –2.567, DF = 50, p =
0.013; apical hyperpallium: t = –2.056, DF = 50, p = 0.045;
olfactory bulb: t = –4.392, DF = 48, p < 0.001). The correlation analysis revealed an expected clear positive correlation between the fat body volume and the total brain
volume of CR (r = 0.908, n = 26, p < 0.001). There were no
significant correlations between the fat body size and the
reduced net brain (net brain without fat, r = –0.271,
p = 0.18) or the reduced structures of cerebellum (r = –0.142,
p = 0.49), tegmentum (r = –0.0147, p = 0.949), bulbus olfactorius (r = –0.0759, p = 0.725) or hyperpallium apicale
(r = –0.174, p = 0.394).
Breeding
Breeding results are presented in Table 2. The average
hatching rate of the (randomly chosen) breeding couples
of the first year (64%) was significantly different to that of
the next two years (86%, 1st year vs. 2nd year: Chi2 = 8.97,
z = 2.995, p = 0.003; 1st year vs. 3rd year: Chi2 = 6.248,
z = 2.5, p = 0.012). The number of unhatched ducklings
10000
Net brain volume [mm3]
9000
8000
Crested Ducks
"Hochbrutflugenten"
Pommeranian Ducks
Abacot Ranger Ducks
7000
6000
5000
a = 0,167
b = 3,183
4000
1000
2000
3000
Body weight [g]
Figure 3. Coronal section through the brain of a Crested Duck
with an intracranial fat body
Frontalschnitt durch das Gehirn einer Landente mit intrakranialem Fettkörper
Arch.Geflügelk. 3/2010
Figure 4. Exemplary double logarithmic plot of net brain
volume vs. body weight. Individual data points, averages and
standard deviations are given for four duck breeds (explanations in the text)
Doppelt logarithmierter Graph als Beispiel für die Beziehung
zwischen Nettohirnvolumen und Körpergewicht. Dargestellt sind
Einzelwerte, Mittelwerte und Standardabweichungen für vier
Hausentenrassen (Erklärungen im Text)
206
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
Table 1. Volumes of brain structures (mm3) and allometric size indices in 4 breeds of domestic ducks (CR = Crested Ducks,
Hb = “Hochbrutflugenten”, Po = Pommeranian Ducks, Ar = Abacot Ranger Ducks (means ± S.D.; * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001)
Hirnstukturvolumina (mm3) und allometrische Größenindices von 4 Hausentenrassen (CR = Landenten mit und ohne Haube,
Hb = Hochbrutflugenten, Po = Pommernenten, Ar = Streicherenten; Mittelwerte ± SD; * p ≤ 0,05, ** p ≤ 0,01, *** p ≤ 0,001)
Crested Ducks
Structure
(n = 26)
Volume
“HochbrutPommeranian
flugenten”
Ducks
(n = 10)
(n = 10)
± 209
4913
± 89.8 4779
± 65.7
± 65.9
Hyperpallium apicale
520
Hyperpallium densocellulare 159
Hyperpallium ventrale
547
Nidopallium
1643
Striatopallidal complex
485
Hippocampus
78.8
Septum
35.9
Prepiriformis
16.4
Bulbus olfactorius
26.8
±
±
±
±
±
±
±
±
±
14.6
3.68
10.7
38.3
14.2
3.14
1.23
0.56
0.59
442
134
479
1520
420
76.8
30.4
12.6
25.4
± 7.11 520
± 2.13 157
± 8.10 547
± 22.9 1623
± 5.73 485
± 1.70
84.5
± 0.63
38.0
± 0.37
15.7
± 0.61
33.6
Telencephalon
Diencephalon
Tractus opticus
Tectum
Tegmentum
Cerebellum
± 76.2
± 6.05
± 2.12
± 4.29
± 10.2
± 11.5
3140
241
63.1
213
633
490
± 39.4 3503
± 4.52 310
± 1.93
80.5
± 3.98 254
± 11.3
759
± 14.3
682
Total brain volume
Net brain volume
6846
5405
3511
293
70.5
232
693
606
± 132
± 123
5814
5589
Abacot Ranger
Ducks
(n = 6)
Indices
Hb + Po + Ar
Crested Ducks
(n = 26)
(n = 26)
± 112
± 153
98.0 ± 1.32
103 ± 1.53
± 9.40 677
± 7.23 171
± 20.4 625
± 36.0 1967
± 12.5 534
± 1.85 72.5
± 0.76 36.0
± 0.48 15.5
± 1.03 33.7
± 8.86
± 8.82
± 17.7
± 42.3
± 7.69
± 3.69
± 1.96
± 1.55
± 2.44
105
102
101
103
101
101
102
99.7
109
±
±
±
±
±
±
±
±
±
2.91
2.45
2.22
2.09
1.69
1.94
1.69
2.68
3.14
96.9
101
97.9
98.4
99.9
101
99.2
103
92.5
± 2.66*
± 2.34
± 1.92
± 2.30
± 3.03
± 4.27
± 3.38
± 3.62
± 2.12***
± 78.0
± 6.65
± 2.79
± 8.46
± 22.4
± 14.2
±
±
±
±
±
±
103
102
104
102
103
105
±
±
±
±
±
±
1.99
1.74
2.33
2.07
1.85
2.24
98.5
98.8
98.0
99.2
97.4
96.3
± 2.15
± 1.98
± 3.04
± 1.86
± 1.45*
± 1.94**
6262
6103
4131
294
71.3
211
735
660
76.4
14.9
2.37
2.84
31.2
42.9
107 ± 3.22*
97.5 ± 1.64*
Table 2. Breeding results (* p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001; significance tests were done for comparison with results from
1st year)
Ergebnisse der Zucht (* p ≤ 0,05, ** p ≤ 0,01, *** p ≤ 0,001; die Signifikanztests wurden im Vergleich mit dem 1. Zuchtjahr durchgeführt)
Breeding year
1st
2nd
3rd
Fertilization rate
Hatching rate
Ducklings with
malformations
Ducklings with motor
incoordination
95%
97%
96%
64%
86%**
86%*
42%
23%**
10%***
25%
19%
17%
with malformations of the skull decreased significantly in
the course of the three years from 42% in the first year to
23% in the second year and to 10% in the third year
(1st year vs. 2nd year: Chi2 = 9.498, z = 3.082, p = 0.002;
1st year vs. 3rd year: Chi2 = 15.713, z = 3.964, p < 0.001).
The number of (hatched) ducklings with behavioral deficits decreased insignificantly as well (1st year: 25%, 2nd
year: 19%, 3rd year: 17%).
Adult ducks occasionally showed skull deformations as
well. These deformations are independent from incoordination of locomotion. Most frequently, perforations of the
skull and encephaloceles were detected. Less frequently,
additionally bone pins between 9 mm–34 mm length were
found. In most cases skull perforations and bone pins were
covered by the cushion of fat and connective tissue under
the crest. The number of adult ducks with skull deformations decreased significantly from 62% in the first year to
36% in the second year (Chi2 = 7.176, z = 2.679, p = 0.007)
(Figure 5).
Discussion
Based on the behavioral results we would like to stress that
it is possible to classify ducks by using an easy test.
Unfortunately, the distribution of the ‘righting time’ data
does not allow a meaningful correlation analysis between
latency to right and fat body size. Most of the data lie
between 0.5 s and 5 s and thus, a necessary data range
lacks. But the other results show, that the proposed ‘righting test’ is able to identify those individuals in a population
that have only slightly difficulties in behavior but exhibit
large fat bodies and presumably a tendency for incoordination of locomotion. These individuals bear the risk of
passing a negative genetic disposition to the next generation. Now, these animals can also be selected by applying
the test presented here and thus could exclude from breeding.
The breeding results demonstrate the appropriateness
of the test and indicate that genetic transmission may play
Arch.Geflügelk. 3/2010
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
100
Number of investigated CR
Ducks without skull deformations
Ducks with skull deformations
80
60
36%
40
62%
20
64%
38%
0
1st year
2nd year
Figure 5. Number of CR with and without skull deformations of
the 1st and 2nd breeding year
Auf Schädelanomalien untersuchte Tiere aus dem 1. und
2. Zuchtjahr.
a key role. This is in agreement with studies where a genetically background of these peculiarities has been assumed
(REQUATE, 1959; LANCASTER, 1990). Thus, the test might
help to reduce the proportion of individuals with suboptimal brains and deficits in locomotion coordination which
is important for the animal welfare discussion.
By analyzing the brain of CR in detail, we observed at
first that an intracranial fat body seems to be a typical neuromorphological peculiarity in Crested Ducks. Presumably
most of CR exhibit such a fat body. The intracranial fat
body has an impact on total brain volume and on net brain
volume. The increased total brain volume of CR is caused
by the fat body. The size of these fat bodies rather than the
existence seems to be a decisive factor for brain composition and behavior. This is in line with findings on free-living
crested Ducks (“Hochbrutflugenten”) living under seminatural conditions, which have fat bodies as well and
which apparently are not negatively influenced in their
survival (FRAHM and REHKÄMPER, 2004). After removing of
the fat body significantly smaller brains are found in CR.
This is due to a reduction of several brain parts, namely the
apicale hyperpallium, olfactory bulb, cerebellum and tegmentum. The olfactory bulb is strictly associated with
olfaction, and the apical hyperpallium is a multimodal
integration centre that serves cognitive functions and is
involved in part in the visual system. These brain parts
should be discussed in other contexts which are not the
major topic here. The tegmentum and cerebellum are
reduced as well and these findings would be in line with
the observed behavioral deficits. The cerebellum can be
regarded as a centre of motor coordination (ITO, 1984). It
receives input from the reticular formation, the vestibular
apparatus and the proprioreceptors. The tegmentum bears
as well many structures that serve as motion control, for
example descending motion pathways including vestibulospinal, reticulospinal and rubrospinal fibers (NIEUWENHUYS
et al., 1998). Comparative neuromorphometry has elucidated a correlation between the size of a brain part and the
function it serves (BENNETT and HARVEY, 1985; REHKÄMPER et
al., 1988; IWANIUK and HURD, 2005) and hence suboptimal
functioning of reduced structures is quite feasible.
Apparently, mostly structures near the common position
of the fat body are affected by reduced volume with respect
to structures with a superficial position (like the olfactory
bulb). Thus, the space demanding process of the fat body
Arch.Geflügelk. 3/2010
207
and the space restriction from the cranium could influence
the size alterations.
There are many Crested Ducks with intracranial fat
bodies but without other noticeable peculiarities and so
this breed represents a good example for the ability of compensation and the plasticity of brains. Besides, fat bodies in
CR have been discussed as being comparable to pathological lipoma found e. g. in humans (BARTELS et al., 2001).
Thus, CR might serve as a model to understand genetically
disposition and functional impact of such lipoma.
An oversized fat body and degenerated brain structures
appear to be the reason of dysfunctions and should be
eliminated. Our breeding experiments have proven a relatively high degree of heritability since only few generations
are needed to increase hatching rates and decrease the
percentage of malformations that are found in CR.
Crested Ducks have a long breeding history and their
occasionally shown problems in motor coordination and
the existence of intracranial fat accumulations are known
since the beginning of the 20th century (KRAUTWALD, 1910).
Thus, their problems should be solved, but without eliminating the whole breed. It is difficult to evaluate the consequences of the extinction of such a breed. Surely, there are
a lot of fancy breeds without an obvious value for economy
or nutrition of people. But, every breed is a cultural heritage and today, inbreeding and selection for more profit
cause as well losing of fitness and adaptability. Species-appropriate keeping conditions and the trend to more animal
welfare could put the old traditional breeds again in focus
due to e.g. their adaptability or their robustness.
Summary
Crested Ducks (CR) are widely bred by poultry fanciers
and are in focus of animal welfare activists, because they
show occasionally intracranial fat bodies, incoordination
of locomotion and high pre- and postnatal mortality. Here,
it is shown that 24 of 26 CR bear such a fat body, but with
a high variability in size (0.3% to 41% of total brain volume). A large fat body could hold responsible for motor
incoordination, thus fat body size seems to be a decisive
factor. A behavioural test helps to identify CR bearing a
problematical fat body. Therefore, ducks were put on their
back and time required to stand up was measured. The
appropriateness of this test has been proven in a special
breeding program. To investigate the influence of fat
bodies on brain composition, an allometrically comparison
of 26 CR brains with those of three uncrested duck breeds
was done.
Ten CR exhibited suboptimal motor coordination. CR
with motor incoordination showed significantly larger fat
bodies and needed significantly more time in the test than
“normal” CR. Total brain volume was significantly larger in
CR, but brain volume minus fat body was significantly
smaller compared to reference breeds. Cerebellum, apical
hyperpallium, tegmentum and olfactory bulb were significantly reduced in CR. Obviously, the behavioural deficits
cannot be explained by the existence of a fat body but by
functionally suboptimal cerebella and tegmenta. The relationship between fat body and reduced structures was discussed.
A breeding experiment with test selected ducks resulted
in increased hatching rate, decreased number of (unhatched) ducklings with skull malformations and as well
decreased number of (hatched) ducks with malformations
or motor incoordination. Thus, this study could be conducive to overcome the criticism of animal welfare activists
without eliminating this old and traditional breed.
208
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
Crested Duck, locomotion incoordination, brain
composition, intracranial fat body, righting test, breeding
strategy, cerebellum
paring the excellent serial sections. The support of the
German Association of Poultry Breeders (BDRG) and the
German foundation for the support of Young Scientists in
Poultry Research (JuWiRa) is kindly acknowledged as
well.
Zusammenfassung
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Key words
Die Hausentenrasse „Landente mit und ohne Haube“ (CR)
zeigt regelmäßig hohe prä- und postnatale Sterberaten,
sowie Schädelanomalien, intrakraniale Fettkörper und
motorische Störungen, die insgesamt als tierschutzrelevant angesehen werden („Qualzucht“). In dieser Untersuchung wird gezeigt, dass 24 von 26 Landenten einen intrakranialen Fettkörper aufweisen, dessen Größe zwischen
0,3% und 41% des Gesamthirnvolumens schwankt. Ein
übergroßer Fettkörper kann für mögliche Bewegungsstörungen verantwortlich gemacht werden und als Hauptstörung angesehen werden.
Es wurde ein einfacher Verhaltenstest entwickelt, der
helfen soll, Tiere mit übergroßem Fettkörper leichter zu
identifizieren. Dafür wurden die Tiere in Rückenlage gebracht und die benötigte Zeit bis zum Aufstehen gemessen.
Der Nutzen dieses Testes wurde in einem speziellen Zuchtprogramm überprüft. Um den Einfluss des Fettkörpers auf
die Hirnzusammensetzung zu untersuchen, wurden die
Gehirne von 26 Landenten allometrisch mit Gehirnen von
drei anderen, glattköpfigen, Hausentenrassen verglichen.
Zehn der 26 CR galten als verhaltensauffällig bezüglich
ihrer Bewegungskoordination.
CR mit Bewegungsstörungen zeigen signifikant größere
Fettkörper als ihre verhaltensunauffälligen Artgenossen
und benötigen auch signifikant mehr Zeit für die Bewältigung des Verhaltenstests. Das Gesamthirnvolumen von CR
ist im Vergleich zu den anderen Hausentenrassen vergrößert, nach Subtraktion des Fettkörpers jedoch signifikant kleiner. Cerebellum, Hyperpallium apicale, Bulbus
olfactorius und Tegmentum sind in CR signifikant kleiner
im Vergleich zu den anderen Rassen. Cerebellum und
Tegmentum sind in die Motorik eingebunden und ihre
Reduktion wird in Zusammenhang mit den Koordinationsproblemen diskutiert.
Bei der Zucht mit positiv vorselektierten Tiere wurde
eine Erhöhung der Schlupfrate erzielt. Zudem ging der
Anteil an Tieren, die im Ei steckengebliebenen waren und
Schädelanomalien zeigten oder nach dem Schlupf Schädelanomalien zeigten zurück. Auch reduzierte sich die
Anzahl an Tieren mit Bewegungsstörungen. Mit dieser
Untersuchung wird ein konstruktiver Beitrag zur Überwindung des Qualzuchtvorwurfs gegenüber den Landenten
geleistet und gleichzeitig zum Erhalt der genetischen Vielfalt bei Haustieren beigetragen.
Stichworte
Haubenente, Bewegungsstörungen, Hirnzusammensetzung, intrakranialer Fettkörper, Umdrehtest, Zuchtmanagement, Cerebellum
Acknowledgements
The authors want to thank Verena Ohms for her support
during the volume measures and Claudia Stolze for pre-
Arch.Geflügelk. 3/2010
Mehlhorn und Rehkämper: Brain alterations and behaviour in Crested Ducks
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Correspondence: J. Mehlhorn, C.&O. Vogt Institute of Brain Research, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf,
Germany, phone: +49 211 8112788, E-Mail address: [email protected]