The goal for most warmblood studbooks is to produce horses that are internationally competitive in sports like show jumping or dressage. The linear scoring system, describing the horse between two biological extremes, is commonly used for a more objective assessment of young horses in many studbooks. However, few studies have examined the phenotypic association between traits linearly scored at a young age and sport performance, and whether there might be an intermediate optimum on the linear scale. This study investigated the phenotypic association between linearly scored traits and competition performance in show jumping or dressage, using the results of linear scoring from young horse performance tests between 2013 and 2021 and competition data between 2014 and 2021 for Swedish Warmblood horses. Sport performance was defined as lifetime accumulated points achieved in show jumping or dressage competitions. Horses were classified as jumping (J) or dressage (D) horses according to their sires’ and grandsires’ classification. In total, 48 linearly scored traits, assessed on a biological scale from A to I, were analyzed. The phenotypic association between the linear score for each trait and sport performance was studied using linear models for sport performance including fixed effects of sex, birth year and linear and quadratic regression on adjusted linearly scored trait values. Significant differences in LS means between J and D horses were found for all linearly scored traits except for length of body and five traits referring to leg conformation. For J horses, 25 linearly scored traits (eight conformation traits, three gait traits, 13 jumping traits and one behavior trait) were found to be significantly associated (p<0.05) with show jumping performance. A majority of these traits (21 out of 25 traits) showed a linear association with performance, indicating that stronger expression (towards A on the assessment scale) was favorable for performance in show jumping in J horses. For D horses, 21 linearly scored traits (eleven conformation traits and ten gait traits) were significantly associated with dressage performance. Most of these traits (15 out of 21 traits) showed a linear association with performance, while six traits showed an association with optimal scores, indicating that breeding for more extreme expression of the specific trait is not associated with better sport performance. These results underline the importance of linearly scored traits as indicator traits of later sport success.

The objective of this study was threefold: 1) To survey the use and impact of foreign stallions in the Swedish Warmblood (SWB) breed 2) To investigate the impact of including genetic groups in the genetic evaluation of the SWB and 3) To estimate the impact of incomplete pedigree information on the estimated breeding values (EBVs) for stallions. Data consisted of 189,330 horses of which 50,907 had performance information. Studbook of origin was determined for stallions with at least 5 progeny tested in Sweden. Those 757 stallions had together 116,505 progeny registered in the SWB. Genetic groups were formed according to preliminary analyses of the genetic levels in dressage and show jumping of the different populations. During the first studied period, comprising horses born before 1980, about 80% of the foals were sired by Swedish born stallions, whereas these only sired 40% of the horses born 1990–2003. In this period Holstein stallions had sired 21% of the foals and Dutch stallions (KWPN) 10%. The proportion of mares covered by foreign stallions increased after the early 1980s to about 80% in 2006. Some of the foreign populations, e.g., Holstein, Selle Francais and KWPN, have significantly affected the show jumping performance level of the SWB breed in the past although the deviation from SWB stallions has become smaller over time. Regarding dressage, no particular foreign population has consistently shown such an impact on the performance although Oldenburg stallions seem to be influential lately. The pedigree completeness (PEC values) of the horses included amounted on average to 0.845 for horses with performance data and to 0.907 for stallions with at least 15 progeny. Foreign stallions had an average PEC value of 0.858. When simulating no pedigree information available for foreign stallions, the EBVs of these stallions changed on average by 19–22 index units, which equals about one genetic standard deviation. Thus, keeping complete and correct pedigree registers is crucial for the assessment of reliable EBVs of SWB horses. Including genetic groups in the genetic evaluation of the SWB resulted in hardly any re-ranking of horses. Correlations between EBVs were about 0.99. Inclusion of genetic groups caused larger standard errors of the EBVs. Furthermore, as the pedigrees on average have great depth, and partially also because Warmblood sport horses have become a mix of many different populations, it was not recommended to include genetic groups in the model for future routine genetic evaluations of SWB.

Genetic correlations between phenotypically similar or related traits tested at young horse performance tests for Danish Warmblood (DWB) and Swedish Warmblood (SWB) horses were calculated using Multi-trait Across Country Evaluation (MACE). Data comprised stallions with an estimated breeding value (EBV) from the national genetic evaluations (NGE) based on at least 10 progeny tested in performance tests, and the ancestors of those stallions in two generations. The DWB data included 349 stallions and the SWB data 426 stallions. Of these, 28 had EBVs in both DWB and SWB. Additionally 151 pedigree animals were common between DWB and SWB. The dependent variables used were NGE results of stallions born 1980 and later, which reduced the number of common stallions with EBVs to 23. The genetic correlations were very high for jumping traits (0.99) and dressage related traits (0.89–0.97). For conformation traits correlations varied between 0.10 and 0.98. Because of the high genetic correlations and frequent use of same or closely related foreign stallions, breeders of both DWB and SWB would benefit from using the NGEs for performance traits across countries, although the genetic correlations do not consider differences in genetic merit levels between the populations. It would be feasible to perform a joint genetic evaluation using MACE, which would improve the reliability of estimated breeding values, and enable ranking of all stallions according to the national scale of each country.

There are two types of 1-day field tests available for young Swedish Warmblood sport horses; one test for 3-year olds and one more advanced test for 4-year olds. Conformation, gaits and jumping ability are evaluated at both tests. Studies on various genetic parameters were based on about 20 000 tested horses. The data for 4-year olds consisted of 30 years of testing. The aims of the study were to estimate genetic parameters for results from different time periods, and to estimate heritabilities for, and genetic correlations between, traits scored in the two tests. The judgement of traits was shown to have been changed during the 30 years of testing, resulting in changes in higher heritabilities in, and stronger genetic correlations between, later time periods. In the first time period, records showed higher residual and lower genetic variances than in the subsequent time periods. Genetic correlations between traits recorded in the first and last time period deviated considerably from unity. Further studies are needed to investigate how to treat data from the early period in genetic evaluations. Heritabilities were moderate to high for conformation traits (0.24 to 0.58) at both types of tests, except for correctness of legs (0.08). The heritabilities for gait traits were also moderate to high (0.37 to 0.53). For jumping traits, the heritabilities ranged between 0.17 and 0.33. The highly positive genetic correlations (0.82 to 0.99) between corresponding traits tested at the simpler test for 3-year olds and at the ridden test of 4-year olds implied that it would be desirable to include the test results of 3-year olds into the genetic evaluation as breeding values for Swedish Warmbloods for many years has only been based on results from 4-year olds.

This paper is one in a series of studies treating the prerequisites for international use of nationally estimated breeding values (EBVs) of sport horse stallions. One prerequisite for effective use of national EBVs across countries (populations) is genetic connectedness among concerned populations. Thus, genetic connectedness between five sport horse populations from breeding organizations in Denmark (DWB), the Netherlands (KWPN), Sweden (SWB) and from the two German breeding organizations Hanover (Han) and Holstein (Holst) was studied. The number of stallions in common (NSC), genetic similarity (GS), variance of the differences between estimated country effects (CEV) in two organizations and correlation between estimates of country effects (CEC) were used as measures of the genetic connectedness between organizations. Stallions with progeny tested in performance tests for young horses in at least one of the five organizations were used. The material included 2457 stallions, born between 1952 and 1997, for which 49446 progeny had been tested in the five breeding organizations. The numbers of stallions with offspring that had been tested in two, three, four and five of the participating organizations were 218, 58, 25 and 5, respectively. The material was arranged into groups according to birth-year of the stallion. Values for NSC, GS, CEV and CEC were calculated for each group to investigate whether there was any difference or trend in genetic connectedness over time. The same measures were also calculated for the whole data-set, considering all available information on pedigrees and progeny. Genetic connectedness was found between all participating organizations in all groups and grew stronger over time. The results were on a similar level to or better than comparable results for Icelandic horses and dairy cattle; they suggest that estimation of genetic correlations between similar traits tested in different organizations is feasible.

The aim of this thesis was to evaluate international sport horse data for use in genetic evaluations both within populations and between populations. An initial review showed that most sport horse producing breed organisations have created young horse testing schemes. Due to moderate to high heritabilities and highly positive genetic correlations with competition results later in life these tests are good tools for selection and suitable for use in genetic evaluations. Efficiency in testing and selection could be improved by including both sexes in young horse tests where this is not yet done, and by shortening tests, where long test periods are practised. Genetic connectedness among populations is an essential prerequisite for any kind of assessments of data between them. Genetic connectedness among the five investigated sport horse populations in this thesis is at such a level that it would be feasible to use their national breeding values based on young horse data in international genetic evaluations for estimation of genetic correlations among similar phenotypic traits. This is possible if correct and internationally unique IDs of horses can be established. Genetic correlations were estimated between phenotypically similar traits tested in Danish Warmblood (DWB) and Swedish Warmblood (SWB). They were highly positive for performance traits and reliabilities for the corresponding breeding values generally became higher when using information from both countries. Thus, mutual use of nationally calculated EBVs was considered possible when stallions are evaluated for use across countries. Moreover a joint genetic evaluation using MACE would be feasible and beneficial for both DWB and SWB. To evaluate how foreign genetic material should be handled in national genetic evaluations, the influence of foreign stallions on the SWB and its genetic evaluation was studied. Origin of stallions has had significant effects on the genetic improvement of jumping traits in SWB. Inclusion of genetic groups in the genetic evaluation resulted in hardly any re-ranking, but less reliable breeding values; hence it was not recommended as a standard procedure. Complete pedigrees of foreign stallions proved to be much more important than genetic grouping to avoid bias in their EBVs.

The aim of this study was to evaluate the genetic connectedness between seven European populations of show jumping horses. Data on stallions bred for jumping and their pedigree up to three generations were provided by seven countries, including 6317 stallions and 22324 different horses. Four different methods were used to estimate the genetic connectedness. Common stallions between countries varied from 0 to 308 and common horses from 130 to 1166. “Genetic similarities” were not the optimal measure of connectedness as number of progeny by country by stallion was not balanced. Correlation between estimates of country effects was computed in a mixed model including the genetic value of horses (h2=0.20, all relationships included). For Germany, Belgium, France and The Netherlands, these correlations were 0.32 to 0.51 corresponding to a balanced scheme with 11 to 19 progeny per stallion per country. Other correlations ranged from 0.08 to 0.27. Another method to evaluate the connectedness was (i) to simulate a systematic difference between the true genetic level of countries, (ii) performing a BLUP and (iii) measuring the percentage of the initial difference that could be found between the estimated genetic levels of the corresponding countries. In 50% of the country pairs, 50% or more of the initial genetic difference was estimated. It was concluded that the genetic connectedness will allow the estimation of genetic correlations.

The purpose of this study was to survey the use of foreign stallions in the Swedish Warmblood (SWB) breed and to investigate how these individuals have influenced the SWB population. Since the early 1980-ies the genetic progress has been 0.85 and 0.53 genetic SD for show jumping and dressage, respectively. An open studbook is practised and foreign stallions have been used over the years to improve different characters of the breed. Data consisted of 202,808 horses included in the SWB routine genetic evaluation for 2006. Studbook of origin was determined for stallions with at least 5 progeny tested in Sweden. Those 757 stallions had together 116,505 progeny registered in SWB. The proportion of progeny sired by foreign stallions born each year has increased since the early 1980-ies, amounting to about 80 % 2006. The most favourable studbooks of origin for show jumping were Selle Français, Holstein and KWPN. For dressage there were not as clear results as for show jumping, but stallions from Oldenburg have had a positive influence during the last 15 years. Inclusion of genetic groups into the national genetic evaluation did not seem to ameliorate the evaluation and is thus not recommended. Introduction As many other European sport horse breeds, the Swedish Warmblood breed traces back to versatile horses used in agriculture or in the cavalry. As the horses gradually became replaced by machines, sport became the new focus for horse breeders. Especially the horses of the cavalry were suitable for this purpose. It was formally decided in 1850 that the Swedish horse should be separated into two breeds, or types: the lighter type, used primarily for the cavalry, and the heavy type, used primarily for farm work. The Swedish Warmblood Association was founded 1928 and 1939 regional studbooks were merged into what today is the Studbook of the Swedish Warmblood horse. The breeding goal for the Swedish Warmblood horse is “to produce a noble, correct and durable riding horse which through its temperament, rideability, good movements and/or jumping ability is internationally competitive”. Importation of foreign genetic material has always occurred and the studbook has never been closed. Foreign influence has increased quite steadily in modern times and today about 80% of the foals born are by foreign stallions (Figure 1), which were imported live into Sweden or serve by imported semen. Session 17 abstract no. 1341 emma.thoren@hgen.slu.se 2 0 10 20 30 40 50 60 70 80 90 19 59 19 62 19 65 19 68 19 71 19 74 19 77 19 80 19 83 19 86 19 89 19 92 19 95 19 98 20 01 20 04 year % p ro ge ny b y fo re ig n st al lio ns Figure 1. Percent progeny sired by foreign stallions per year The national genetic evaluation of Swedish Warmblood horses includes results from performance tests of young horses as well as results from dressage and show jumping competitions. Consequently the EBVs for show jumping and dressage are integrated BVs estimated with a multitrait BLUP animal model, where the competition traits are representing the breeding goal. Since the early 1980-ies the genetic progress has been 0.85 and 0.53 genetic SD for show jumping and dressage, respectively (Figure 2). 75 80 85 90 95 100 105 110 19 69 19 71 19 73 19 75 19 77 19 79 19 81 19 83 19 85 19 87 19 89 19 91 19 93 19 95 19 97 19 99 20 01 20 03 birth year BV

Results from performance tests and competitions of young horses are used by major European warmblood horse breeding associations for genetic evaluations. The aim of this review was to compare genetic parameters for various tests of young horses to assess their efficiency in selection for dressage and show-jumping. Improved understanding of genetic information across countries is also necessary, as foreign trade with semen is rapidly increasing. The review is based on inquiries to European breed associations and on (17) scientific publications available, which have analysed genetic parameters of young horse data and/or relationships between young and mature horse results in sport.Despite differences in testing methods of young horses, results for major horse populations were in good agreement. Specially designed young horse performance tests, including stallion tests, showed high heritabilities and high genetic correlations with later competition results. We recommend that test results are encouraged to be used across countries for genetic evaluation of imported stallions and semen. Short station tests are generally preferred when selecting stallions for both dressage and jumping traits, whereas competition data may be used when selecting for only one discipline. We also recommend that extensive field testing of young horses is encouraged and should include both genders.