Genetic correlations between dressage,show jumping and studbook‐entry inspection traits in a process of specialization in Dutch Warmblood horses

Sport performance in dressage and show jumping are two important traits in the breeding goals of many studbooks. To determine the optimum selection scheme for jumping and dressage, knowledge is needed on the genetic correlation between both disciplines and between traits measured early in life and performance in competition in each discipline. This study aimed to estimate genetic parameters to support decision‐making on specialization of breeding horses for dressage and show jumping in Dutch warmblood horses. Genetic correlations between performance of horses in dressage and show jumping were estimated as well as the genetic correlation between traits recorded during studbook‐entry inspections and performance in dressage and show jumping competitions. The information on competition comprised the performance of 82 694 horses in dressage and 62 072 horses in show jumping, recorded in the period 1993–2012. For 26 056 horses, information was available for both disciplines. The information on traits recorded at studbook‐entry inspections comprised 62 628 horses, recorded in the period 1992–2013. Genetic parameters were estimated from the whole dataset and from a subset without horses recorded in both disciplines. Additionally, the genetic parameters were estimated in three different time periods defined by horses' birth year. The genetic correlation between dressage and show jumping in the whole dataset was ?0.23, and it was ?0.03 when it was estimated from horses recorded in only one discipline. The genetic correlation between dressage and show jumping was more negative in the most recent time period in all the cases. The more negative correlation between disciplines in more recent time periods was not reflected in changes in the correlations between competitions traits and the traits recorded in the studbook‐first inspection. These results suggest that a breeding programme under specialization might be most effective defining two separate aggregate breeding goals for each of the disciplines.     

Genetic connections between dressage and show-jumping horses in Dutch Warmblood horses

Abstract

During the last decades, the breeding practice within the Dutch Warmblood studbook (KWPN) has resulted in an increasing specialisation of horses into show-jumping (JH) and dressage (DH). The objective of this study was to describe the effect of the specialisation on the connectedness between the subpopulations of JH and DH horses registered by KWPN. The subpopulations comprised 23,800 JH horses and 18,125 DH horses, born between 1995 and 2009. Genetic similarity (GS), genetic pool in common (GC_x) based on the marginal genetic contribution of common ancestors and coefficient of relationship (r) between and within subpopulations were analysed in three periods of time to describe changes in genetic connectedness between subpopulations. A decline in GS (0.97–0.45), GC_0.5 (0.69–0.13) and r (0.018–0.014) in the recent years was observed. Both subpopulations have a common genetic pool; however, if the specialisation process continues, it will result in two unrelated (genetic) groups.     

Analysis of competition performance in dressage and show jumping of Dutch Warmblood horses

Most Warmblood horse studbooks aim to improve the performance in dressage and show jumping. The Dutch Royal Warmblood Studbook (KWPN) includes the highest score achieved in competition by a horse to evaluate its genetic ability of performance. However, the records collected during competition are associated with some aspects that might affect the quality of the genetic evaluation based on these records. These aspects include the influence of rider, censoring and preselection of the data. The aim of this study was to quantify the impact of rider effect, censoring and preselection on the genetic analysis of competition data of dressage and show jumping of KWPN. Different models including rider effect were evaluated. To assess the impact of censoring, genetic parameters were estimated in data sets that differed in the degree of censoring. The effect of preselection on variance components was analysed by defining a binary trait (sport‐status) depending on whether the horse has a competition record or not. This trait was included in a bivariate model with the competition trait and used all horses registered by KWPN since 1984. Results showed that performance in competition for dressage and show jumping is a heritable trait (h² ~ 0.11–0.13) and that it is important to account for the effect of rider in the genetic analysis. Censoring had a small effect on the genetic parameter for highest performance achieved by the horse. A moderate heritability obtained for sport‐status indicates that preselection has a genetic basis, but the effect on genetic parameters was relatively small.     

Genetic relations of movement and free-jumping traits with dressage and show-jumping performance in competition of Dutch Warmblood horses

Genetic parameters for traits evaluated at the studbook entry inspection and genetic correlations with dressage and show-jumping performance in competition were estimated. Data comprised 36,649 Warmblood horses that entered the studbook between 1992 and 2002. The genetic analyses were performed using univariate and bivariate animal models. Heritabilities of the studbook entry traits were estimated in the range 0.15–0.40. The movement traits showed moderate to strong mutual genetic correlations, whereas the genetic correlations of movement traits with free-jumping traits were weak to moderate. The free-jumping traits showed strong to very strong mutual genetic correlations.

Competition results of 33,459 horses with performance in dressage and 30,474 horse with performance in show-jumping were linked to the studbook entry data to estimate the genetic relationship with performance in competition. Heritability estimates for dressage and show jumping were 0.14. Genetic correlations of the movement traits with dressage were moderate to strong, and with show-jumping weak to moderate. Genetic correlations of the free-jumping traits with dressage were weak to moderate and unfavourable. The free-jumping traits were genetically strong to very strong correlated to show-jumping. It was concluded that a selection of the traits evaluated at the studbook entry inspection will favourably contribute to estimation of breeding values for sport performance.     

Random regression model estimation of genetic parameters for show‐jumping results of Hungarian Sporthorses

The aim of this study was to estimate the genetic parameters for show‐jumping competition performance of Hungarian Sporthorses using a random regression model. There were 21 210 records from 739 horses collected in Hungary between 1996 and 2004. Performance was expressed as shifted Blom normalized ranks and as the difference between fence height and fault points. The random regression model (RRM) included fixed effects for sex, year, location, and obstacle height and random effects for animal, rider and permanent environment. Regressions for the random effects in the RRM were modelled with Legendre polynomials from first to fifth order of fit. The model focused on performance of horses from 4 to 11 years of age, with heterogeneous residual variances considered. The heritabilities were low to moderate for both variables. Genetic and phenotypic correlations between different ages decreased with increasing distance between the ages.     

Improvement in the national genetic evaluation of warmblood riding horses by including information from related studbooks

Abstract

Young horse performance test data from two warmblood riding horse populations, Norwegian warmblood (NWB) and Swedish warmblood (SWB), were analysed to examine whether including information from a related studbook would increase the accuracy of the genetic evaluations within a population. Ten conformation and performance traits from 31,588 horses, 774 NWB and 30,814 SWB were analysed separately and jointly using single trait animal models. Heritabilities were moderate to high, and varied from 0.15 (conformation, joint data) to 0.74 (jumping technique, NWB data). The genetic similarity (GS) between populations was 31%, with the SWB, as expected given the size of the populations, contributing most to the GS (98%). Genetic correlations between the same traits in the two populations were 0.43–0.90 but with large standard errors (0.2–0.3). Including information from the other population increased the average accuracy of estimated breeding values for common stallions, on average 4% for SWB and 110% for NWB.     

Consequences of specialized breeding in the Swedish Warmblood horse population

In many European warmblood studbooks, clear specialization toward either jumping or dressage horses is evident. The Swedish Warmblood (SWB) is also undergoing such specialization, creating a possible need for separate breeding programs and a discipline-specific Young Horse Test (YHT). This study investigated how far specialization of the SWB breed has proceeded and the potential consequences. Individuals in a population of 122,054 SWB horses born between 1980 and 2020 were categorized according to pedigree as jumping (J), dressage (D), allround (AR), or thoroughbred (Th). Data on 8,713 J horses and 6,477 D horses assessed for eight traits in YHT 1999–2020 were used to estimate genetic parameters within and between J and D horses and between different periods. Future scenarios in which young horses are assessed for either jumping or dressage traits at YHT were also analyzed. More than 80% of horses born in 1980–1985 were found to be AR horses, while 92% of horses born in 2016–2020 belonged to a specialized category. The average relationship within J or D category was found to increase during the past decade, whereas the relationship between these categories decreased. Heritability estimates for gait traits were 0.42–0.56 for D horses and 0.25–0.38 for J horses. For jumping traits, heritability estimates were 0.17–0.26 for J horses and 0.10–0.18 for D horses. Genetic correlations between corresponding traits assessed in J and D horses were within the range 0.48–0.81, with a tendency to be lower in the late study period. In the future scenarios, heritability and genetic variance both decreased for traits that were not assessed in all horses, indicating that estimation of breeding value and genetic progress for these traits could be affected by a specialized YHT. However, ranking of sires based on estimated breeding values (EBVs) and accuracy of EBVs was only slightly altered for discipline-specific traits. With continued specialization in SWB, specialization of the YHT should thus be considered.     

Heritability of foot conformation and its relationship to sports performance in a Dutch Warmblood horse population

Reasons for performing study: Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future performance, but reduce the risk of injuries and lameness. Negative conformational traits, such as asymmetrical or ‘uneven’ forefeet would possibly diminish performance. Objectives: To assess the prevalence and heritability of uneven feet and its genetic relationship to other conformation traits as well as to sporting performance later in life in Warmblood riding horses. Methods: The databases of the Royal Dutch Warmblood Studbook (KWPN, n = 44,840 horses) and Royal Dutch Equestrian Sports Federation (KNHS, n = 33,459 horses in dressage and n = 30,474 horses in showjumping) were linked through the unique number of each registered horse. Therefore, heritabilities and genetic and phenotypic correlations could be estimated from the scores of the jury at studbook admission and the sports performance of that population in dressage and jumping over the period 1990–2002. Results: The prevalence of uneven feet was 5.3% on average, and increased from under 4.5% during the first 3 years of recording to over 8% in the years from 2000 onwards. Heritability estimates of foot conformation traits were moderate and ranged from 0.16 for heel height to 0.27 for hoof shape. The genetic correlation between the trait of uneven feet and performance in competition was negative but weak: ?0.09 with dressage and ?0.12 with showjumping. Conclusions: Predisposition to uneven feet can be reduced by selection. Because of weak genetic correlations, the increased prevalence is not directly associated with selection for better sports performance or higher conformation grade. If the trait ‘uneven feet’ arises from a disproportionate relationship between height at the withers and neck length, then selection on conformation grade might result in development of uneven feet. In general, limb conformation has a moderate genetic relationship to conformation grade and foot conformation traits have a genetic relationship to sporting performance. Reducing occurrence of uneven feet by selection is possible, without limiting progress in sport performance.     

Estimation of genetic parameters of conformation traits in Iranian Thoroughbred horses

The aim of this study was to estimate the genetic parameters of conformation traits in Iranian Thoroughbred race horses. The data set included the conformation records of 607 Thoroughbred horses. In this study, 10 conformation traits were recorded. The effect of sex was significant for length of back line (P < 0.05), withers height (P < 0.05), circumference of front cannon (P < 0.001), and circumference of hind cannon (P < 0.001). The effect of age was significant for all traits (P < 0.01). The genetic parameters were estimated by the restricted maximum likelihood (REML) method using DFREML program. The heritability estimates were for head length 0.39, length of back line 0.41, length of shoulder 0.24, heart girth 0.49, chest width 0.22, withers height 0.38, front cannon height 0.27, circumference of front cannon 0.30, hind cannon height 0.29 and circumference of hind cannon 0.34. The estimates of genetic correlation ranged from 0.18 to 0.96 and those of phenotypic correlation varied from 0.16 to 0.83.     

Prevalence of various radiographic manifestations of osteochondrosis and their correlations between and within joints in Dutch Warmblood horses

Reasons for performing study: Osteochondrosis (OC) is the most important orthopaedic developmental disorder in horses and may manifest in several different forms. No detailed study on the prevalence and/or interrelation of these forms is available, even though these data are a prerequisite for conclusive genetic studies. Objectives: To assess the prevalence of the various manifestations of OC as detected radiographically and to evaluate possible relationships between their occurrence within the same joint and between different joints. Methods: The FP (femoropatellar), TC (tarsocrural) and MCP/MTP (metacarpophalangeal/metatarsophalangeal) joints of 811 yearlings selected randomly, descending from 32 representative stallions, were radiographed and scored for the presence and grade of osteochondrotic lesions. Results were compared at the sire, animal, joint and predilection site levels. Results: In the FP joint, the percentage of animals showing normal joint contours in all sites was 60.7%. For the TC joint and the combined MCP/MTP joints, these figures were 68.6 and 64.6%, respectively. For all joints combined, the percentage dropped to 30.5%. Sedation improved detection of OC lesions in the FP joint. There was a high correlation between the right and left joints. The correlation between flattened bone contours and fragments was considerably less. Conclusions: Scoring on a detailed scale is necessary to achieve good insight into the prevalence of OC. Observations on the right and left joints can be combined in further analyses, whereas flattened bone contours and fragments should be evaluated as statistically different disorders. Potential relevance: This study provides insight into the prevalences of various manifestations of OC and their relationships, within and between joints. These results form the basis for detailed quantitative and/or molecular genetic studies that should lead to the establishment of breeding indices and/or genetic marker sets for OC.     

An epidemiological study of myopathies in Warmblood horses

REASON FOR PERFORMING STUDY: There are few detailed reports describing muscular disorders in Warmblood horses. OBJECTIVES: To determine the types of muscular disorders that occur in Warmblood horses, along with presenting clinical signs, associated risk factors and response to diet and exercise recommendations, and to compare these characteristics between horses diagnosed with polysaccharide storage myopathy (PSSM), those diagnosed with a neuromuscular disorder other than PSSM (non-PSSM) and control horses. METHODS: Subject details, muscle biopsy diagnosis and clinical history were compiled for Warmblood horses identified from records of biopsy submissions to the University of Minnesota Neuromuscular Diagnostic Laboratory. A standardised questionnaire was answered by owners at least 6 months after receiving the muscle biopsy report for an affected and a control horse. RESULTS: Polysaccharide storage myopathy (72/132 horses) was the most common myopathy identified followed by recurrent exertional rhabdomyolysis (RER) (7/132), neurogenic or myogenic atrophy (7/132), and nonspecific myopathic changes (14/132). Thirty-two biopsies were normal. Gait abnormality, 'tying-up', Shivers, muscle fasciculations and atrophy were common presenting clinical signs. Forty-five owners completed questionnaires. There were no differences in sex, age, breed, history or management between control, PSSM and non-PSSM horses. Owners that provided the recommended low starch fat supplemented diet and regular daily exercise reported improvement in clinical signs in 68% (19/28) of horses with a biopsy submission and 71% of horses diagnosed with PSSM (15/21). CONCLUSIONS: Muscle biopsy evaluation was a valuable tool to identify a variety of myopathies in Warmblood breeds including PSSM and RER. These myopathies often presented as gait abnormalities or overt exertional rhabdomyolysis and both a low starch fat supplemented diet and regular exercise appeared to be important in their successful management. POTENTIAL RELEVANCE: Warmbloods are affected by a variety of muscle disorders, which, following muscle biopsy diagnosis can be improved through changes in diet and exercise regimes.     

Evaluation of cervical radiographs in Dutch Warmblood horses,using a novel radiographic grading system for the cervical articular process joints

Clinical and radiographic examination of the cervical spine has been of increasing interest in the prepurchase examination and clinical work-up conducted for horses. The objective of this study was to describe a grading system useful for evaluating all the cervical articular process joints (cAPJs). Additionally, the findings of the cervical radiographs (occiput, cAPJ and intercentral joint space grading, intra- and intervertebral sagittal ratios, and intervertebral disc width measurements) were reported, and their association with clinical complaints in a large group of Dutch Warmblood horses (n = 598) were investigated. Significant associations were found between cAPJ radiographic grades and clinical complaints using the chi-squared test (C2-3 [P = 0.01], C5-6 [P = 0.006], C6-7 [P < 0.001], and C7-T1 [P = 0.02]). Higher occiput grades were significantly associated with clinical complaints (chi-squared test, P = 0.005). A large variability was found for intra- and intervertebral ratios and minimum intercentral joint space in the control group, but no significant association between intercentral joint space and clinical complaints was observed using the Kruskal–Wallis test followed by post hoc testing with the Wilcoxon rank sum test with a Bonferroni correction. The main limitations of this study were that only information regarding localisation was used for the statistical analyses, without any other details of the clinical complaints. Furthermore, clinical records were retrospectively reviewed, and a bias towards cervical findings in the clinical data recordings should be considered. It was concluded that knowledge of the distribution of the radiographic findings evaluated in this study and their associated clinical relevance can be useful in reaching a science-based diagnosis in daily practice.     

党参复方添加剂对运动马血清生化指标的影响

试验旨在研究党参复方添加剂对健身骑乘用的运动马血清生化指标的影响.将60匹健康的运动马随机分为4组,分别在基础精料中添加0、0.5％、1.0％、1.5％的中药添加剂,饲养60d.结果显示:与对照组相比,添加1.0％党参复方添加剂,运动马血清碱性磷酸酶(ALP)和血清肌酸激酶(CK)含量显著降低(P＜0.05);血清葡萄...     

Influence of foot conformation on duration of competitive life in a Dutch Warmblood horse population

Reasons for performing study: Warmblood horse studbooks aim to breed horses with a conformation that will enable elite future sports performance, but reduce the risk of early retirement due to lameness. Negative conformational traits, such as asymmetrical or ‘uneven’ forefeet may possibly shorten the career of sporthorses. Objectives: To investigate the significance of foot conformation at young age to duration of the career of sporthorses. Methods: Databases of the Royal Dutch Warmblood Studbook (KWPN) and of the Royal Dutch Equestrian Sports Federation (KNHS) were matched and resulted in a dataset comprising 23,116 records of horses for which their conformation scores and duration of their sports career were available. Survival analysis was used to determine which of the conformation traits had a significant effect on duration of sports career in dressage and jumping at basic and elite level. Results: Duration of competitive life was shorter for jumping than for dressage. A different set of risk factors was found for each level and discipline. The trait ‘uneven feet’ tended to shorten the competitive life in dressage, but was a significant risk factor at the elite level of jumping. Conclusions: Limb conformation and, in particular, the conformation of the distal limb, are important for duration of competitive life. From the prevalence of uneven feet in sports disciplines, it may be concluded that this is an undesirable trait, particularly at the elite level of jumping, since uneven feet have a detrimental effect on the duration of competitive life in a sporthorse population. Potential relevance: This study provided evidence that the conformation trait uneven feet has a negative effect on Warmblood jumping performance and, therefore, breeders should be encouraged to avoid this phenomenon at foal age.     

Modelling genetic evaluation for dressage in Pura Raza Español horses with focus on the rider effect

The most popular use of the Pura Raza Español horse in sport is for dressage competitions. Tests on young sport horses were first established in 2004 in Spain to collect data for the genetic evaluation of this breed's suitability for dressage. The aim of this study was to compare eight different models to find out the most appropriate way to include the rider in the genetic evaluation of dressage. A progressive removal of systematic effects from model was also analysed. A total of 8867 performance records collected between 2004 and 2011 from 1234 horses aged between 4 and 6 years old were used. The final score in the dressage test was used as the performance trait. The pedigree matrix contained 8487 individuals. A BLUP animal model was applied using a Bayesian approach with TM software. The horse's age, gender, travelling time, training level, stud of birth and event were included as systematic effects in all the models. Apart from the animal and residual effects that were present in all models, different models were compared combining random effects such as the rider, match (i.e. rider–horse interaction) and permanent environmental effects. A cross‐validation approach was used to evaluate the models' prediction ability. The best model included the permanent environmental, rider and match random effects. As far as systematic effects are concerned, the event or the stud of birth was essential effects needed to fit the data.     

Genetic conditions of joint Nordic genetic evaluations of lifetime competition performance in warmblood sport horses

Breeding programmes for warmblood sport horses are similar in the Nordic countries Sweden, Denmark, Finland and Norway, and stallions of same origin are used. The aim was to investigate whether a joint Nordic genetic evaluation based on lifetime competition performance is feasible and beneficial for breeding competitive sport horses in the Nordic countries. Results for almost 45 000 horses in show jumping and 30 000 horses in dressage were available. The larger populations in Sweden and Denmark contributed with 85% of the results. Heritabilities and genetic correlations between performances in the different countries were estimated, and comparisons of accuracies of estimated breeding values (EBVs) and number of stallions with EBVs based on national or joint data were studied. The heritabilities ranged between 0.25 and 0.42 for show jumping and between 0.14 and 0.55 for dressage. The genetic correlations between competition performances in the Nordic countries were estimated to 0.63–1.00. EBVs based on joint data increased accuracies for EBVs for stallions by 38–81% and increased the number of available stallions with EBVs by 40–288%, compared to EBVs based on national data only. A joint Nordic genetic evaluation for sport horses is recommended.     

Ultrasonographic description of the caudal and ventral lung borders in normal Warmblood horses

The aim of the study was to describe the caudal and ventral lung border in clinically normal horses more precisely than it had been described previously and also to resolve the contradictions of data published in standard textbooks. Twenty‐two healthy Warmblood horses were used in the study. The lung border was determined by 2‐dimensional ultrasonography at the following anatomical levels: tuber olecrani, tuberositas deltoidea of the humerus, tuberculum majus of the humerus, tuber ischiadicum and ventral, mid‐ and dorsal points of the tuber coxae. Examinations were performed bilaterally at the end of inspiration and expiration. Distances between the actual lung borders and corresponding anatomical levels were measured and compared statistically. The results showed that the olecranon could not be used as an anatomical landmark. Instead, the deltoid tuberosity could be used as an alternative, as the lung border was found in the 7th intercostal space (ICS) in 14 horses and in the 8th ICS in 8 horses. The lung border at the level of the tuberculum majus was found in the 10th ICS in every horse. At the level of the tuber ischiadicum, the lung border was detected equally in the 14th (11 horses) and 15th (11 horses) ICS. At the level of the ventral and midpoint of the tuber coxae, the lung border was found in the 15th or 16th ICS. No lung border was found at the level of the dorsal point of the tuber coxae or in the 17th ICS.