[Analysis of environmentally-conditioned and genetic influences on the frequency of hip joint dysplasia in German Shepherd dogs].

The importance of environmental and genetic influences on the frequency of hip dysplasia was studied in 10,595 German shepherd dogs. Systematic effects were analysed using mixed linear and mixed nonlinear threshold models. Following effects were regarded in the models applied: sire and mother of the dog as random effects, age at x-raying, sex, birth year and season of the x-rayed dogs, litter size, percentage of x-rayed dogs in each litter and sex ratio of the litter as fixed effects. Sire, mother, sex and age at x-raying showed significant influence on the occurrence of hip dysplasia. The heritability estimates in a hierarchical data design (sire, mother within sire) for the polychotomous trait hip dysplasia were for full sibs h2 = 0.30, for maternal half sibs h2 = 0, 48, and for paternal half sibs h2 = 0.11. Only the heritability estimates of the paternal half sibs seem to be reliable because kennel and breeder effects are confounded with the mother effect. Analysing the frequency of hip dysplasia as all-or-none traits, the heritability estimates were usually lowered by 50%. Selection programmes to reduce frequency of hip dysplasia can be improved if the estimation of breeding values with respect to environmental effects and frequency of hip dysplasia in all relatives will be implemented.