The genetic contribution to canine personality.

The domestic dog may be exceptionally well suited for behavioral genetic studies owing to its population history and the striking behavior differences among breeds. To explore to what extent and how behavioral traits are transmitted between generations, heritabilities and genetic correlations for behavioral traits were estimated in a cohort containing over 10,000 behaviorally tested German shepherd and Rottweiler dogs. In both breeds, the pattern of co-inheritance was found to be similar for the 16 examined behavioral traits. Furthermore, over 50% of the additive genetic variation of the behavioral traits could be explained by one underlying principal component, indicating a shared genetic component behind most of the examined behavioral traits. Only aggression appears to be inherited independently of the other traits. The results support a genetic basis for a broad personality trait previously named shyness-boldness dimension, and heritability was estimated to be 0.25 in the two breeds. Therefore, breeds of dogs appear to constitute a valuable resource for behavioral genetic research on the normal behavioral differences in broad personality traits.

Canine hip dysplasia: study of heritability in 401 litters of German Shepherd dogs.

Heritability of hip dysplasia was estimated to be about 0.4 to 0.5 when based on the radiographic evaluations of the hip joints of 2,404 German Shepherd Dogs born at The Armed Forces Dog Training Center in Sweden. The material included all dogs in 401 litters born at the Center from 1965 through 1973 that reached the age of 15 months. To be expected with such high heritability, frequency of hip dysplasia in the offspring was shown to be affected by the hip joint status of sire and dam as well as by the hip joint status of their parents and littermates. Even matings between sires with normal hip joints and dams with only slight dysplasia resulted in significantly higher frequency of hip dysplasia in the offspring, when compared with the frequency if both sires and dams had normal hip joints. Frequency of hip dysplasia in the progeny of sires with normal hip joints varied greatly. Since 1973, selection of the breeding stock has been based on hip joint status (phenotype) of the breeding animals and of their relatives as well as on what had become known about frequency of hip dysplasia in the litters already born (progeny testing). In this way, frequency of hip dysplasia in 347 dogs born at the Center during 1975 was lowered to 28%. This figure should be compared with the figure of 50%, which represents the frequency of hip dysplasia in the kennel up to 1970, when selection was not as strict as could be expected in a well-controlled kennel.