Genetic and phenotypic trends in canine hip dysplasia in the German population of German shepherd dogs

Phenotypic and genetic trends were examined in 157,455 German shepherd dogs of the German population born between 1985 and 2003 which were Xrayed for canine hip dysplasia (CHD). A subset of 40,270 dogs born between 1998 and 2003 was examined for which information was available on age at examination and X-raying veterinary practitioner. Relative breeding values were predicted using best linear unbiased prediction methods (BLUP) and Gibbs Sampling. There was an almost linear and significant decline in both phenotypic and genetic trends for CHD scores (scale 1 to 5 for CHD free to severe CHD) over a period of 19 years, with b = -0.021 +/- 0.002, and b = -1.69 +/- 0.05, respectively. After introduction in 1999 of a selection scheme based on relative breeding values (RBVs, mean 100, standard deviation 20) of a linear animal model, phenotypic and genetic trends declined less than before 1999, with b = -0.019 +/- 0.011 and b = -1.43 +/- 0.29. Analysis of the effects of RBVs of parental combinations among sires and dams on the percentage of non-affected progeny showed that lower RBVs were associated with a higher percentage of non-affected progeny than were higher RBVs. In addition, it was also shown that selection procedures based on RBVs are more efficient than selection schemes based on phenotypic records of parents. When the maternal RBV was above 100, the proportion of non-affected progeny was between 10% and 20% lower than when the maternal RBV was below or equal to 100. There was a significant relationship between higher inbreeding coefficients and higher RBVs of the animal.