Conformation affects health of sport horses

L. Jönsson^{1 *}, A. Näsholm¹, L., Roepstorff², A. Egenvall³, G. Dalin² and J. Philipsson¹

¹Department of Animal Breeding and Genetics, ²Department of Equine Sciences, ³Department of Clinical Sciences, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden.

Few population studies have been performed regarding associations between conformation and soundness of horses. The objective was to investigate phenotypic and genetic associations between conformation and health status in young riding horses. Analyses included 8,187 horses examined for conformation and health by independent examiners during the Swedish Riding Horse Quality Test (RHQT) of 4-5-year-old horses. Both descriptive conformation traits and assessment scores of overall conformation were studied. Single trait linear models and multi-trait animal models were used, for phenotypic effects and genetic correlations. Four major health indicators were constructed from the detailed veterinary examinations. Conformation assessment scores were all favourably related to at least one of four studied health traits, both phenotypically and genetically. Best health status was found for intermediate sized horses, with well-positioned neck, light front, and no limb deviations. Correct movements in trot were also important. Among limb deviations stiff pasterns, toe-out/toe-in forelimbs, and small/large hock angles had negative effects on health. Genetic correlations reached 0.75 between conformation scores for head-neck-body and health, and 0.43 for limb scores and health. Heritabilities of withers height, cannon bone circumference and overall scores (except for limbs), were medium to high, 0.20-0.67. For specific limb deviations present in ≥2% of examined horses, heritabilities were 0.01-0.15. Considerable heritabilities of conformation and favourable correlations to health indicate good opportunities for genetic improvements of conformation, and to some extent health, except for some limb deviations.