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Estimation of genetic population variables for six radiographic criteria of hip dysplasia in a colony of Labrador Retrievers

Stefanie OhlerthDepartment of Small Animal Radiology, University of Bern, Länggasse 124+128/Bremgartenstrasse 109a, 3012 Bern, Switzerland.
Present address is Department of Veterinary Surgery, University of Zörich, Winterthurerstrasse 260, 8057 Zörich, Switzerland.

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Johann LangDepartment of Small Animal Radiology, University of Bern, Länggasse 124+128/Bremgartenstrasse 109a, 3012 Bern, Switzerland.

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André BusatoDepartment of Animal Breeding, University of Bern, Länggasse 124+128/Bremgartenstrasse 109a, 3012 Bern, Switzerland.
Present address is Maurice E. Möller Foundation, Murtenstrasse 35, PO Box 8354, 3008 Bern, Switzerland.

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Claude GaillardDepartment of Animal Breeding, University of Bern, Länggasse 124+128/Bremgartenstrasse 109a, 3012 Bern, Switzerland.

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Abstract

Objective—To estimate genetic population variables for 6 radiographic criteria of canine hip dysplasia (CHD).

Animals—664 full- and half-siblings from a colony of Labrador Retrievers.

Procedure—Heritability estimates and genetic correlations were calculated for 6 radiographic criteria of CHD. Two evaluation protocols were compared: the grade of the most severely affected hip joint and the sum of the scores for both hip joints. The predictive performance of estimated breeding values was also evaluated.

Results—The overall prevalence of CHD (Fédération Cynologique Internationale grades C, D, and E) was 29.6%. Median age at radiographic examination was 377 days. Heritability for the total CHD grade, Norberg angle (NA), coverage of the femoral head (COV), craniodorsal acetabular rim (ACR), subchondral bone sclerosis (SUBCH), shape of the femoral head and neck (FHN), and osteoarthritic changes at the insertion site of the joint capsule (JC) was estimated as follows: 0.44, 0.43, 0.46, 0.37, 0.32, 0.21, and 0.05, respectively. Heritability estimates were slightly higher for the sum of the scores for both hip joints. If NA and COV were included as fixed effects in the model for the dependent variables ACR, SUBCH, FHN, and JC , then heritability of these traits significantly decreased (0.08 to 0.15). High scores of NA and COV lead to a significant increase of the scores of the remaining criteria.

Conclusions and Clinical Relevance—Canine hip dysplasia is heritable to a moderate degree. Signs of subluxation revealed the highest heritability estimates. The criteria ACR, SUBCH, FHN, and JC were strongly influenced by NA and COV. (Am J Vet Res 2001;62:846–852)

Abstract

Objective—To estimate genetic population variables for 6 radiographic criteria of canine hip dysplasia (CHD).

Animals—664 full- and half-siblings from a colony of Labrador Retrievers.

Procedure—Heritability estimates and genetic correlations were calculated for 6 radiographic criteria of CHD. Two evaluation protocols were compared: the grade of the most severely affected hip joint and the sum of the scores for both hip joints. The predictive performance of estimated breeding values was also evaluated.

Results—The overall prevalence of CHD (Fédération Cynologique Internationale grades C, D, and E) was 29.6%. Median age at radiographic examination was 377 days. Heritability for the total CHD grade, Norberg angle (NA), coverage of the femoral head (COV), craniodorsal acetabular rim (ACR), subchondral bone sclerosis (SUBCH), shape of the femoral head and neck (FHN), and osteoarthritic changes at the insertion site of the joint capsule (JC) was estimated as follows: 0.44, 0.43, 0.46, 0.37, 0.32, 0.21, and 0.05, respectively. Heritability estimates were slightly higher for the sum of the scores for both hip joints. If NA and COV were included as fixed effects in the model for the dependent variables ACR, SUBCH, FHN, and JC , then heritability of these traits significantly decreased (0.08 to 0.15). High scores of NA and COV lead to a significant increase of the scores of the remaining criteria.

Conclusions and Clinical Relevance—Canine hip dysplasia is heritable to a moderate degree. Signs of subluxation revealed the highest heritability estimates. The criteria ACR, SUBCH, FHN, and JC were strongly influenced by NA and COV. (Am J Vet Res 2001;62:846–852)