GENETIC DISPOSITION OF BONE-DISEASES IN S PORT HORSES

The target of this study was to estimate the genetic parameters of bon e diseases in sport horse breeding. Therefore radiographs of 3566 auct ion horses of seven German breeding associations were evaluated by two veterinarians. The results of the analysis show that bone diseases as navicular disease and bone spavin are more frequent than the other de fects. The estimated heritabilities are low to medium, between 0.02 an d 0.18. Also genetic correlations between the defects and performance criteria such as riding and jumping ability are insignificant. This le ads to the conclusion that bone diseases are more influenced by enviro nmental effects and therefore selection against bone diseases will hav e only little effect. Various alternatives were studied to consider se lection for bone diseases in breeding programs for riding horse popula tions. The calculations show that selection against orthopaedic defect s will not significantly improve physical constitution, but genetic pr ogress of performance traits like rideability and jumping will be redu ced. To prevent genetic deterioration of bone diseases it is advisable to exclude stallions from breeding with respect to those orthopaedic defects showing significant and frequent deviations from the standard. Therefore all horse breeding associations should monitor the physical constitution of their horse population based on random samples of sir es progeny groups. But first of all, breeders and owners should optimi ze the environment in raising and training for their horses to reduce the significance of bone diseases considerably.