Orthopaedic health, conformation and longevity in riding horses

Abstract: Soundness and longevity of the riding horse play a central role for animal welfare, sport performance and horse owner economy. Routine registration of health traits in horses is rare. Thus, knowledge of genetic variation in health of horses and long term effects on longevity is scarce. The major aims of this thesis were to estimate prevalence and heritability of orthopaedic health findings, and genetic and phenotypic relationships between orthopaedic health, conformation and longevity in the Swedish warmblood horse. The included studies I-IV were based on standardised documentation of health and conformation at the Riding Horse Quality Test (RHQT) of 8238 tested 4-5-year-old horses, participating during 1983-2005. Longevity was measured as number of years in competition (NYC), and lifetime performance results from official competitions (LPERF) during 1983-2012. Results show that conformation significantly influences health status of the horse, and that both health and conformation of the young horse influence future longevity and success in competition, both phenotypically and genetically. Longevity was generally better in horses with good young horse health regarding palpatory orthopaedic health, locomotion, hooves and assessed overall orthopaedic health. Effusions were the most common clinical health finding, whereas severe acute findings were relatively rare. Horses with flexion test reactions had significantly lower chances of competing later in life compared to horses without reactions. Regarding conformation, intermediate sized horses with high scores for type and head-neck-body conformation, light front and correct movements in trot at hand were found most important. Also, the assessed talent of a young horse was influenced by the health and conformation, both for dressage and jumping. Good health was genetically correlated with better longevity at a level of 0.3, with similar correlations between high conformation scores and longevity. Heritabilities of palpatory orthopaedic health and hooves were estimated at 0.10-0.14, and between 0.20-0.36 for overall conformation traits, except for limbs at 0.06. Considerable genetic variation of conformation and to some extent of health, and generally favourable associations between health, conformation, longevity and performance, suggest possibilities to improve health traits if considered in breeding.