Quantitative genetics of traits associated with hip dysplasia in a canine pedigree constructed by mating dysplastic Labrador Retrievers with unaffected Greyhounds

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Abstract
Objective—To determine the genetic influence on expression of traits associated with canine hip dysplasia. Animals—193 dogs from an experimental canine pedigree. Procedure—An experimental canine pedigree was developed for linkage analysis of hip dysplasia by mating dysplastic Labrador Retrievers with nondysplastic Greyhounds. A statistical model was designed to test the effects of Labrador Retriever and Greyhound alleles on age at detection of femoral capital epiphyseal ossification, 8-month distraction index, and 8-month dorsolateral subluxation score. Results—The additive effect was significant for age at detection of femoral capital epiphyseal ossification. Restricted maximum likelihood estimates (± SD) for this trait were 6.4 ± 1.95, 10.2 ± 2.0, 10.8 ± 3.1, 11.4 ± 2.1, and 13.6 ± 4.6 days of age for Greyhounds, Greyhound backcross dogs, F1 dogs, Labrador Retriever backcross dogs, and Labrador Retrievers, respectively. The additive effect was also significant for the distraction index. Estimates for this trait were 0.21 ± 0.07, 0.29 ± 0.15, 0.44 ± 0.12, 0.52 ± 0.18, and 0.6 ± 0.17 for the same groups, respectively. For the dorsolateral subluxation score, additive and dominance effects were significant. Estimates for this trait were 73.5 ± 4.1, 71.3 ± 6.5, 69.1 ± 6.0, 50.6 ± 12.9, and 48.4 ± 7.7%, respectively, for the same groups. Conclusions—In this canine pedigree, traits associated with canine hip dysplasia are heritable. Phenotypic differences exist among founder dogs of each breed and their crosses. This pedigree should be useful for identification of quantitative trait loci underlying the dysplastic phenotype. (Am J Vet Res 2002;63: 1029–1035)