Reproduction and Health in Holstein Warmblood Mares

Home , Friesian horse, Holsteiner, Yorkshire Coach Horse

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

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 fitness- associated 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

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.

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.

CHAPTER ONE

Inbreeding depression in horses: A review

L. Roos and J. Krieter

Institute of Animal Breeding and Husbandry, Christian-Albrechts-University, Kiel, Germany

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.

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).

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,

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 (F i, 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

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 (N e) (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): . Studies by Meuwissen and Woolliams (1994) revealed fundamental relationships between the effective population size, inbreeding depression and the genetic variances of fitness traits, respectively. They concluded that the critical size for N e, 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

inbreeding has appeared (Gómez et al., 2009). The ΔFi coefficients share the properties of ΔF (Falconer and Mackay, 1996) and, contrary to the F i 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).

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 lifetime reproductive 1.00 performance a) Cothran et al. (1984) Standardbred horse 318 conception rate, foaling rate 10.3 (trotters), 7.40 (pacers) Langlois and Blouin (2004) French Warmblood, 535,746 b) numeric productivity 1.01 French Coldblood (declared foalings) 1.02 Sevinga et al. (2004) Frisian horse 52,392 retained Placenta 15.6 – 15.7 c) (mean ΔF= 1.90) Wolc et al. (2006) Thoroughbred 2,033 twinning n.s. Sairanen et al. (2009) Finnhorse, 32,731 foaling rate 3.60 Standardbred Trotter 33,679 foaling rate 9.90 Wolc et al., (2009) Warmblood 3,965 foaling rate 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 Morphology and conformation 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 morphological traits 10.3 Sierszchulski et al. (2005) Arabian 706 morphological traits 0.88 Gómez et al. (2009) Andalusian horse 16,472 morphological traits 8.20 (mean ΔF= 1.00) Performance Klemetsdal, (1998) Norwegian Trotter 7,866 racing performance 5.50 a) 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 b) Declarations of mating c) Mean inbreeding coefficients of the foals born in 1999 and 2000, respectively d) Mean level of inbreeding for the potential offspring, mares and stallions, respectively

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).

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).

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 (N e) 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

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).

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 (F i) 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 F i were around 10 times higher than those for ΔFi. The parameter δ was also negative

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 20 th 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 (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

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. Non- genetic 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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CHAPTER TWO

Investigations into genetic variability in Holstein

Horse breed using pedigree data

L. Roos 1, D. Hinrichs 1, T. Nissen 2 and J. Krieter 1

1Institute of Animal Breeding and Husbandry, Christian-Albrechts-University, Kiel, Germany

2Verband der Züchter des Holsteiner Pferdes e.V., Abteilung Zucht, Kiel, Germany

Accepted for publication in Livestock Science

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

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 19 th 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.

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 Schleswig-

Holstein” 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).

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 C sire and C dam 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 n i 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.

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

(f e), 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 (f a) 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 (f g) 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

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 (F a) was computed as:

= () + 1 − ()() + () + (1 − ())/2 where F a 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.

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 (N e) 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 [N e = 1/(2 ∆F)].

Increased inbreeding coefficients (∆F) were computed with:

− ∆F = 1 − where F t and F t-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.

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.

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 Ancestors to explain 75% of gene pool, n 52 Ancestors to explain 80% of gene pool, n 78 Ancestors to explain 90% of gene pool, n 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).

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 , possibly influence 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

Inbreeding coefficient 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 (F a) (Ballou, 1997) 2.14 2.23 16.66

Effective population size and genetic c ontributions

The effective population size was calculated as the average effective population size of the two generations included in the reference population. The estimated N e 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 effectiv e animals from 1950 to the year

2000. The most conspicuous decline is shown between 1960 and 1980 (Figure 2).

A slight increase of N e from 49.45 (until 2000) to 61.18 animals ( 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% 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 W armblood horses made up 40.12 % of the reference population under study.

At 25.98 %, the Engli 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 es timated with 16.38%. The most influential G erman breed was the Hanoverian 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 fore ign breeds (%) to the Holstein W armblood 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 Thoroughbr eds 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).

Table 3 Genetic contributions (%) of the 15 most influential stallions in the Holstein

Warmblood reference population

Year Total Marginal Stallion of birth contribution 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

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).

Figure 4 Development of marginal genetic contributions (%) of the mo st formative sires in Holstein W 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 fo und for the L- line (Ladykiller xx) and the comparatively low represented A -line (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 th e most affecting female ancestors (Table 4).

Table 4 Genetic contributions (%) of the 10 fundamental breeding mares in the

Holstein Warmblood reference population

Year Total Marginal Mare of birth contribution 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.

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

inbreeding coefficient was expected compared with the Hanoverian Warmblood breed.

The average effective populations size (N e) 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.

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 20 th 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

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 (f e) and the effective number of ancestors (f a) could be used as a further evidence for the random loss of genetic diversity.

A ratio f e/ f a 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 (f g = 16.78) and the effective number of ancestors (f a= 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 (N e) 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

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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CHAPTER THREE

Effect of inbreeding on female fertility in Holstein horse breed

L. Roos 1, C. Heuer 1, D. Hinrichs 1, T. Nissen 2 and J. Krieter 1

1Institute of Animal Breeding and Husbandry, Christian-Albrechts-University, Kiel, Germany

2Verband der Züchter des Holsteiner Pferdes e.V., Abteilung Zucht, Kiel, Germany

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

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.

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.

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

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 + stallion o) 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: inbrcoef i = inbreeding coefficient of covered mare or expected foal

(linear covariable), season j = combined effect of month and year of mating, firstageclass k = age class of mare’s age at first mating in lifetime and ageclass l = age class of mare’s age at mating.

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

(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

Model 1 * Model 2** Age class n LSQ s.e. LSQ 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

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.

Table 2 LSQ-means (LSQ) and standard error (s.e.) by the age of the mare at mating

(age class) for the occurrence of stillbirth in the two different models

Model 1 * Model 2** Age class n LSQ s.e. LSQ s.e. 1 ( ≤ five years of age) 26,774 0.024 ± 0.003 0.025 ± 0.003

2 (six to 10 years of age) 29,936 0.026 ± 0.003 0.027 ± 0.003

3 (10 to 16 years of age) 18,064 0.028 ± 0.003 0.029 ± 0.003

4 (> 16 years of age) 7,001 0.035 ± 0.004 0.037 ± 0.004

*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)

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%.

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).

Table 3 LSQ-means (LSQ) and standard error (s.e.) by the age of the mare at mating

(age class) for the outcome of the season’s first mating in the two different models

Model 1 * Model 2** Age class n LSQ s.e. LSQ s.e. 1 ( ≤ five years of age) 39,587 0.402 ± 0.024 0.396 ± 0.023

2 (six to 10 years of age) 44,546 0.374 ± 0.023 0.360 ± 0.022

3 (10 to 16 years of age) 29,853 0.339 ± 0.022 0.324 ± 0.021

4 (> 16 years of age) 13,698 0.291 ± 0.020 0.275 ± 0.019

*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)

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

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 (h 2 = 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

Stallion Mare Add. genetic (mare/foal) Trait 2 / / h Model 1 (Mare as basic individual) Foaling rate 0.422 0.109 0.051 0.013 0.096 0.024 ± 0.026 1) ± 0.006 ± 0.006 ± 0.001 ± 0.008 ± 0.002

Stillbirth 0.028 0.0069 0.356 0.089 0.274 0.069 ± 0.019 ± 0.005 ±0.133 ± 0.031 ± 0.103 ± 0.025

First mating 1.091 0.233 < 0.001 < 0.001 0.279 0.059 outcome ± 0.067 ± 0.011 ± 0.000 ± 0.000 ± 0.016 ± 0.003

Model 2 (Expected foal as basic individual) Foaling rate 0.409 0.109 0.087 0.023 0.129 0.033 ± 0.026 ± 0.006 ± 0.005 ± 0.003 ± 0.014 ± 0.003

Stillbirth 0.025 0.006 0.572 0.146 0.033 0.008 ± 0.026 ± 0.006 ± 0.112 ± 0.025 ± 0.090 ± 0.022

First mating 1.039 0.219 0.116 0.024 0.254 0.054 outcome ± 0.068 ± 0.011* ± 0.016 ± 0.003 ± 0.033 ± 0.007

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).

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

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

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

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.,

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

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

(h 2 = 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 (h 2 = 0.069) is in the range of estimates for other fertility disorders such as early abortion (h 2 = 0.05, Klemetsdal and Johnson, 1989). Estimating heritability for stillbirth in cattle, Hinrichs et al. (2011) computed a value of h 2 = 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

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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0388.2006.00575.x.

CHAPTER FOUR

Standardisierte Erfassung von Gesundheitsdaten beim Holsteiner Pferd

L. Roos und J. Krieter

Institut für Tierzucht und Tierhaltung, Christian-Albrechts-Universität, Kiel, Deutschland

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, sofern in Zuchtprogrammen zukünftig auf

Gesundheitsdaten zurückgegriffen werden soll. Die Hälfte der beteiligten

Tierarztpraxen (n=11) stellten Diagnosedaten der von ihnen betreuten

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.

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.

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;

Nikoli ć, 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.

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.

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.

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.

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 Schleswig-

Holstein 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.).

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 wenig standardisiert, vielfach noch handschriftlich und meist ohne direkte Nutzung einer EDV-gestützten

Dokumentation. Eine nachträgliche elektronische 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.

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).

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

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

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 Praxis-

EDV 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 über entsprechende Schnittstellen und

Eingabemöglichkeiten, unter Einbindung der Praxis–EDV bei definierten

Zugangsrechten und unter Wahrung größtmöglicher 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.

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Anhang A1 Diagnoseschlüssel zur Erfassung von Gesundheitsdaten beim Pferd (Roos, 2011, unveröffentlicht)

Schlüsselnr. Organsystem/Diagnose/Behandlung 3.4. Leukozytenerkrankungen 1. 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 4. 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 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

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 Katarrhalische und entzündliche Erkrankungen des 5.12. Tumoren 8.2. 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 Kaumuskeln, Kiefergelenk, Speicheldrüse, 6. 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 8. Magen- Darm- Trakt 8.14. Viszerale Neuropathie 10.6. Harninkontinenz 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

10.10. Tumoren 12.8.2. Tumoren und Missbildungen 15.5. Sonstiges 10.11. Harnblasenruptur 12.8.3. Penislähmung 10.12. Sonstiges 12.8.4. Sonstiges 16. Endokrine Erkrankungen Erkrankungen der Hypothalamus- Hypophysen- 16.1. Nebennierenrinden- Achse 11. Hernien 13. Fortpflanzungsstörungen beim Hengst 16.1.1. Dysfunktion der Pars intermedia 11.1. Hernia diaphragmatica 13.1. Störungen der Hodenfunktion 16.1.2. Equines Cushing Syndrom Hypothalamus- Hypophysen- Nebennierenrinden- 11.2. Hernia umbilicalis 13.2. Störungen der Nebenhodenfunktion 16.2. Achse Veränderungen der Akzessorischen Störungen der Nebenschilddrüse und 11.3. Hernia funiculi umbilicalis 13.3. Geschlechtsdrüsen 16.3. Kalziumhomöostase 11.4. Hernia inguinalis incarcerata 13.4. Sonstiges 16.4. Erkrankungen des endokrinen Pankreas 11.5. Hernia scrotalis interstitialis 16.5. Sonstiges weiblichen Geschlechtsorgane, 11.6. Hernia femoralis 14. Fortpflanzungsstörungen Morphofunktionelle Veränderungen des 11.7. Hernia abdominalis 14.1. Genitaltraktes 17. Nervensystems 11.8. Hernia perinealis 14.1.1. Kongenitale Unfruchtbarkeit 17.1. nicht infektiöse Krankheiten 11.9. Sonstiges 14.1.2. Krankheiten des äußeren Genitale 17.1.1. Gehirnerschütterung 14.1.3. Erkrankungen im Hymenalbereich 17.1.2. Gehirnquetschung 12. männliche Geschlechtsorgane 14.1.4. Erkrankungen der Vagina und der cervix uteri 17.1.3. Dummkoller 12.1. Kryptorchismus 14.1.5. Erkrankungen des Uterus 17.1.4. Ataxie 12.2. Erkrankungen des Hodens 14.1.5.1. Endometritiden 17.1.5. Cauda- equina- Syndrom Aseptische und eitrige Hoden- und 12.2.1. Nebenhodenentzündungen 14.1.5.2. Nachgeburtsverhalten 17.1.6. Epilepsie 12.2.2. Hodentumoren 14.1.5.3. Sonstiges 17.1.7. Narkolepsie 12.3. Erkrankungen des Samenstranges 14.1.6. Erkrankungen des Eileiters 17.2. Krankheiten der peripheren Nerven Erkrankungen und funktionelle Störungen der 12.4. Hydrocele 14.1.7. Ovarien 17.2.1. Paralytische Geschehen 12.5. Varikocele 14.1.8. Zwillingsträchtigkeit 17.3. Infektionskrankheiten des Zentralnervensystems Trächtigkeitsverlust durch embrionalen Fruchttod und 12.6. Hämatocele 14.1.9. Aborte 17.3.1. EHV I und IV 12.7. Erkrankungen des Skrotums und des Präputiums 14.2. Erkrankungen der Milchdrüse 17.3.2. Aujeszkysche Krankheit 12.7.1. Wunden, Phlegmone, Abszesse 17.4. Bornaviren- Infektion 12.7.2. Tumoren 15. Infektionskrankheiten der Geschlechtsorgane 17.5. Tollwut 12.7.3. Posthitis 15.1. EHV I - IV 17.6. Flaviviren 12.7.4. Phimose/Paraphimose 15.2. Salmonellenabort 17.6.1. West- Nile- Fieber 12.8. Erkrankungen des Penis 15.3. Contagiöse Equine Metritis (CEM) 17.6.2. Frühsommer- Meningoenzephalitis 12.8.1. Wunden und Entzündungen 15.4. Beschälseuche 17.6.3. Tetanus

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. Krankheiten der Hornhaut Angeborene /kongenitale Anomalien des Auges 18.8. Malleus 19.7.12. Parafilariose 20.4.1. 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 19. Parasitosen 19.12. Haarlingsbefall 20.7.1. Linsentrübung 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

20.10. Krankheiten des Augapfels und der Augenhöhle 24. Brust- und Lendenwirbelsäule 26.4.8. Sonstiges 20.10.1. Entzündungen der Orbita 24.1. Frakturen 20.10.2. Verletzungen in der Augenhöhle 24.2. Spondylose 27. Beckengliedmaße 20.10.3. Orbitalphlegmone 24.3. Tumoren 27.1. Krankheiten des Oberschenkels 20.10.4. Exophtalmus 24.4. Sonstiges 27.1.1. Wunden 20.10.5. Endophtalmus 27.1.2. Myopathien und Parese Missbildungen und angeborene Defekte des Augapfels 20.10.6. und der Augenhöhle 25. Schwanzwirbelsäule 27.1.3. systemische Muskelkrankheiten 20.11. Sonstiges 25.1. Frakturen 27.1.4. Coxitis akuta 25.2. Tumoren 27.1.5 HD 21. Ohr 25.3. Sonstiges 27.1.6 Luxatio femoris 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. Krankheiten des Karpalgelenkes 27.3.5. Hahnentritt Verletzungen der Haut und der Sehnenscheiden am 23.2. Luxation 26.4.1. 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. OC/OCD am Sprunggelenk Rehbein (Überbein im Bereich des 23.7. Osteomyelitis der Wirbelsäule 26.4.6. Luxationen 27.4.3. Sprunggelenkes) 23.8. Sonstiges 26.4.7. Sehnenrupturen 27.4.4. Entzündungen des Sprunggelenkes

27.4.5. Wunden 30.2. Krongelekserkrankungen 31.21. Strahlfäule 27.4.6. Hygrops des Sprunggelenkes 30.2.1. OC/ OCD im Bereich des Krongelenks/ Kronbeins 31.22. Sonstiges Wunden und Entzündungen der Sehnenscheiden am 27.4.7. 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

Anhang A2 Checkliste zu Haltung und Fütterung (nach Beyer, 1998, verändert)

I. Haltung/Betreuung 1. Größe der Liegefläche (m 2) a) Einzelbox (min. 16 m 2)

b) Gruppenbox (min. 12m 2/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 Frei begehbare Paddocks: Pferde etc.) 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 Anzahl/Art der Maßnahmen: bei Heuvorlage/beim Fegen z.B. Anfeuchten des Bodens etc. 8. Lichteinfall/Helligkeit der Stallung Fensterfläche m 2/Grundfläche m 2 ? 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)

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

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 (N e) 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 (N e) in conjunction with a stagnating

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 N e, 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

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.

The values of heritability for all of the studied traits are calculated at a low level

(h 2 ≤ 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

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

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(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.

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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 (N e).

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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 (N e = 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

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correspondent database, a consistent key system, maximum data security and predefined rules of data access and usage should be ensured.

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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.

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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 (N e). Zusätzlich sollten Fremdblutanteile und genetische Beiträge einflussreicher Gründertiere berechnet werden. Bei moderater Inzucht und niedriger effektiver Populationsgröße (N e = 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 Daten mittels Datenbank. Ziel war die modellhafte

Entwicklung und Erprobung einer flächendeckenden Phänotypisierung von

Diagnosen und Befunden aus der Pferdemedizin. Ein unzureichender Datenrücklauf seitens der Züchter und Veterinäre verdeutlicht eine gewisse Skepsis bezüglich des

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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.

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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.

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112

LEBENSLAUF

Name: Lukas Philipp Roos Geburtsdatum: 20.08.1981 Geburtsort: Speyer/Rhein Familienstand: ledig Staatsangehörigkeit: 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 Christian- Albrechts- 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

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