ANS 378 Animal Genetics
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Research Journal Report #04
11/23/04
Research Topic: Effects of Inbreeding
Animal Species: Canine
Title of the Paper: Population structure, inbreeding trend and their association with hip and elbow dysplasia in dogs
Author(s): Mäki, K.; Groen, A. F.; Liinamo, A. E.; Ojala, M.
Abstract: The aims of this study were to examine population structure and inbreeding trend in six dog breeds in Finland and to assess the inbreeding depression for hip and elbow dysplasia. Data consisted of 289 569 dogs, of which 36 924 dogs also had a record for hip and/or elbow dysplasia screening. From the early 1980s onwards, inbreeding trends were decreasing in the Golden Retriever, the Labrador Retriever, the Rough Collie and the Rottweiler, probably as a result of importations of dogs, and somewhat increasing in the Finnish Hound and the German Shepherd. When analysed per generation, observed mean inbreeding coefficients were higher than the expected ones in each breed, indicating that breeders have not actively avoided inbreeding. As a class effect, the inbreeding level was significant only for hip dysplasia in the Labrador Retriever and the German Shepherd breeds. As a regression, inbreeding level of a dog had only a minor effect on both of the dysplasias. Hip dysplasia in the Labrador Retriever appeared to be more influenced by longer term aggregation of homozygosity (long-term inbreeding) in animals than by shorter-term inbreeding. When analysed from two data sets with a minimum of five and two ancestral generations for each dog in the data, a statistically significant association between hip dysplasia and inbreeding for the Labrador Retriever could be detected only in the former data set.
Keywords: Dogs, elbow dysplasia, hip dysplasia, inbreeding depression, population structure.
Reference: Mäki, K., A. F. Groen, A. E. Liinamo, and M. Ojala. 2001. Population structure, inbreeding trend and their association with hip and elbow dysplasia in dogs. Anim. Sci. 73:217-228.
Purebred dogs today often suffer from genetic disorders – effects of inbreeding, bad selection, or other possible factors. Among the problems facing many breeds is elbow and hip dysplasia. This disease generally only shows up later in the life of a dog, and is identified as a deterioration of the joints, many times leading to painful arthritis. The authors of this paper studied inbreeding in populations of six purebred breeds of dog (the Finnish Hound, German Shepherd, Golden Retriever, Labrador Retriever, Rough Collie, and Rottweiler) in Finland from 1978 to 1999. In total, 289,569 dogs were screened for the presence of elbow and/or hip dysplasia. Dogs were selected based on their pedigree and the number of complete generations that could be traced. From this, an inbreeding coefficient was calculated for each dog. Dysplasia data was also collected, and a score was assigned to each animal based on the severity of the disease. Other factors such as the age of the dog, the experience of the x-raying veterinarian, the birth year and sex of the dog, and the effect of the panelist responsible for classifying the radiographs were also considered. Observed data collected were compared with data obtained from computer simulations.
The purpose of this research was to try to determine if there was an inbreeding depression effect for hip and/or elbow dysplasia in specific breeds of dogs. If a correlation was found between inbreeding and the later presentation of either of the dysplasias, actions could be taken to help alleviate future cases of the disease, possibly by implementing more rigid breeding guidelines.
Due to the homozygosity caused by inbreeding, it was found that dogs with a greater inbreeding coefficient are more likely to be affected by hip and/or elbow dysplasia. Until the early 1980s, inbreeding coefficients increased in each of the breeds studied, after which a slight decline was observed. This decline was most likely due to the importation of new animals into the breeding population, and new regulations that were instituted pertaining to some of the breeds. However, only in the Labrador Retriever and the German Shepherd were the inbreeding levels significant.
Studies such as these have great importance for breeders who are trying to improve the quality of their animals. Knowing the effect their current breeding programs have on their animals, allows for future planning, whether they wish to keep on with their current system, or alter their methods (if necessary) to enhance their breed of dog. Information obtained from this study does not only affect dogs in Finland, but has applications worldwide in the pedigree dog community. If an example can be set in one country, similar breeding restrictions/methods could feasibly be used in other countries, as well, in an effort to improve the genetic quality of all purebred dogs.
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