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Wallin, L., Strandberg, E., & Philipsson, J. (2003). Genetic correlations between field test results of Swedish Warmblood Riding Horses as 4-year-olds and lifetime performance results in dressage and show jumping. Livestock Production Science, 82(1), 61–71.
Abstract: The main objective of this study was to estimate genetic correlations between traits of young sport horses (4 years old) evaluated in the Swedish Riding Horse Quality Test (RHQT) and later competition results in dressage and show jumping. The data comprised 3708 Warmblood horses born between 1968 and 1982 that had participated in the RHQT as 4-year-olds and 25[punctuation space]605 horses born between 1953 and 1995 with competition records. According to the criteria between 1206 and 1879 horses were common to this two files and were available for the estimations of the genetic correlations. Competition performance traits were cumulative points and cumulative placings received during a horse's lifetime, and a log10 transformation was used to achieve a more normal distribution of the data. Genetic correlations between gait traits scored in the RHQT and competition results in dressage were favourable, in the range 0.63-0.75, and between jumping traits scored in the RHQT and results in show jumping 0.83-0.93. Estimated heritabilities for gait and jumping traits scored in the RHQT were in the range 0.09-0.27 and 0.10-0.18, respectively. Estimated heritabilities for the cumulative points and cumulative placings in dressage and show jumping were 0.17/0.16 and 0.23/0.27, respectively. Thus, the results from the RHQT have proved to be useful for early genetic evaluation and selection of both mares and stallions for sport performance traits.
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Wallin, L., Strandberg, E., & Philipsson, J. (2001). Phenotypic relationship between test results of Swedish Warmblood horses as 4-year-olds and longevity. Livestock Production Science, 68(2-3), 97–105.
Abstract: The relationship between longevity and different traits scored in the Swedish Riding Horse Quality Test (RHQT) was studied to evaluate their use as predictors of survival. Data comprised 1815 Warmblood horses born between 1969 and 1982 that had participated in the RHQT as 4-year-olds. Survival information was obtained via a questionnaire sent to owners of horses that had participated in the RHQT between 1973 and 1986. All phenotypic values of traits scored at 4 years of age were adjusted for the effect of place/year (event). Survival analysis was performed taking into account censoring. Traits having significant effects on longevity were: conformation, legs (included in conformation), orthopaedic status, jumping ability, and the horses' combined classification score for dressage and jumping talents, respectively. Orthopaedic health had the greatest influence on longevity, and demonstrated the importance of judging health traits in young sports horses. The results of this study confirmed that there is a significant phenotypic relationship between many of the RHQT traits and longevity, and thus the possibility of using them as predictors of survival.
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Koenen, E. P. C., van Veldhuizen, A. E., & Brascamp, E. W. (1995). Genetic parameters of linear scored conformation traits and their relation to dressage and show-jumping performance in the Dutch Warmblood Riding Horse population. Livestock Production Science, 43(1), 85–94.
Abstract: In this study genetic parameters of linear scored conformation traits of the Dutch Warmblood Riding Horse were estimated in relation to performance in competition. Observations on 10 665 mares were analyzed with an animal model including the fixed effects age, classifier, location and percentage of thoroughbred. Using restricted maximum likelihood algorithms, heritabilities of 26 linear scored conformation traits were estimated in the range 0.09-0.28. Several conformation traits had high up to very high mutual genetic correlations. Competition results of 3476 horses with performance in dressage and 3220 horses with performance in show-jumping were linked to the conformation data to estimate the genetic relationship between conformation and performance in competition. The model for the evaluation of the competition results included the fixed effects riding club, age and sex. Estimated heritabilities for dressage and show-jumping were 0.17 +/- 0.05 and 0.19 +/- 0.04, respectively. Genetic correlations between conformation and performance were low to moderate. The length of the neck, length and position of the shoulders, shape and length of croup and muscularity of the haunches had a significant moderate genetic correlation with dressage. Muscularity of the neck, shape of the croup and muscularity of the haunches had a significant genetic correlation with show-jumping. The results indicate that, due to the low genetic correlations with performance traits, indirect selection for performance using conformation results is of limited value.
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Art, T., & Lekeux, P. (2005). Exercise-induced physiological adjustments to stressful conditions in sports horses. Adaptability of sport horses to stressful conditions, 92(2), 101–111.
Abstract: Among athletic/sports animals, the horse has a unique ability to increase its oxygen uptake by a factor of 60 during heavy exercise. This is achieved by physiological adaptations of all the links in the oxygen chain. Ventilation is increased by a factor of 30. Since the horse is a compulsory nasal breather, this hyperpnea necessitates high transmural pressure changes, which may be responsible for the dynamic collapse of the airways. Blood flow is increased by a factor of 10. Since the left ventricle is not very compliant, this increase necessitates a high filling pressure in the pulmonary circulation, which may induce capillary stress failure and exercise-induced pulmonary haemorrhage. Lastly, oxygen transport is improved by splenic contraction which increases haemoglobinemia by 50%. Sports horses frequently suffer from several problems, which are related either to endogenous or exogenous stresses experienced during their career. These stresses, caused by the use of the horse as a competition animal, may lead to several medical problems. At a systemic level, endogenous stresses include hyperkaliemia, lactacidemia, and hyperthermia; oxidative stress may induce problems at a general, and/or a pulmonary level. External factors, e.g. poor quality of inspired air, transport, hot and humid ambient conditions, and microbiological agents, may also induce abnormal body attacks, and lead to health problems.
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