Genetic analysis of stifle arthrosis in Swedish boxer dogs :

Abstract: Stifle problems in Boxer dogs have been a major issue in discussions in Swedish boxer breeding circles for a long time. Since 1997, the Swedish Kennel Club (SKC) has a ge-netic health programme for boxers to reduce the number of dogs affected by stifle arthrosis. This study is based records from the SKC on radiographic evaluations of stifle, elbow and hip joints of Swedish boxer dogs between the years 1989 to May 2005. The number of radiographed stifle joints, hip joints and elbow joints were 3990, 4197 and 390, respec-tively. This material was merged with a pedigree file including 26943 boxers. The study also contains information and statistics on insured boxers from the insurance company Agria From 1992 to 2005 the proportion of Boxers with stifle arthrosis has decreased from 18% to 6%. The proportion of radiographed dogs has increased during the period studied from 36% in 1992 and was in 2005 about 65% of the registered Boxers. The number of regis-tered boxers in Sweden during the last fifteen years has been stable around 550 dogs per year. To be able to estimate how much of the phenotypic variation in a trait that depends on genetic variation the heritability must be calculated. The genetic analysis of this material showed heritabilities for stifle arthrosis of 0.11 ± 0.04 and for hip dysplasia (HD) 0.28 ± 0.03. There were significantly more male dogs affected of stifle arthrosis than female dogs. Furthermore, there was a significantly higher risk of stifle arthrosis and HD with increased age at screening. For HD, the effect of test year was also significant. The ge-netic correlation between stifle arthrosis and HD was not different from zero (0.09 ± 0.14). The number of boxers with elbow dysplasia (ED) was very low and only few had been radiographed. Therefore, in this study ED has not been analysed. The material from the insurance company Agria showed that the numbers of boxers with stifle related problems decreased, but not as much for all other breeds. The number of boxer owners that were paid for their dogs’ life insurance due to stifle problems de-creased more than for all other breeds. Since the start of SKC:s health programme there has been a steadily decreasing trend of young Boxer affected with stifle arthrosis. In the statistics from the insurance company Agria the status of the elderly Boxers are more likely to be represented. The decreasing of stifle arthrosis in this material is not that large as for all other breeds. In the future it is of great importance to the Boxer dogs in Sweden to continue the radio-graphic screening of stifle joints. Furthermore, one should in the breeding programme only use breeding animals that not are affected with stifle arthrosis and actively evaluate the progenies of these animals regarding the status of the stifle arthrosis.