Genetic evaluation of horses for performance in dressage competitions in Great Britain

Genetic evaluation of sport horses for dressage competition and estimation of breeding values are performed in many Northern European countries. To date, no such system has been used in GB. The aim of this study was to estimate genetic parameters for performance in dressage competition and then to predict breeding values for horses competing in dressage in GB using an animal model. The percentage of marks awarded was used as the performance measure. Random effects comprised additive genetic, horse permanent environment, class, event and class–event interaction. Horse gender, age, height and competition standard were included as fixed effects. In a second model, breed class was added as a fixed effect. Heritability (SE) of performance in the two models was 0.15 (0.018) (no breed) and 0.11 (0.036) (including breed). In both models age was significantly associated with performance (P < 0.001), with performance peaking at age 10. Stallions performed significantly better than geldings. A significant association between performance and height was detected only in the model which did not include breed effects. The model including breed was considered to be the most appropriate, given the nature of the sport horse population in GB. It should be possible to predict breeding values of sufficient accuracy.