Genetic analysis and effect of inbreeding on skeletal diseases and echocardiography measurements in Italian Boxer dogs

The dog is the non human species for which the largest number of genetic disorders is known. The objectives of this study were to estimate genetic parameters for two skeletal diseases (SP: spondylosis deformans; HD: hip dysplasia) and one echocardiography measurement (AA: area of the aortic annulus) associated to the risk of subaortic stenosis and to assess the effect of inbreeding on these traits in the Italian Boxer dog population. Data included screening results, obtained by the Centre for the Screening of Skeletal Diseases, for SP and HD of 6,730 and 2,987 dogs respectively (examined from 1993 to 2008 for HD and from 1997 to 2009 for SP). Data on AA included measures of 1,024 random Italian Boxer dogs which were submitted to a complete echocardiographic examination from 1999 to 2004. The outcome variables were: the degree of osteophytes development (four-grade linear system) for SP and the FCI (Fédération Cynologique Internationale) 5-class linear grades for HD. A Bayesian analysis was implemented via Gibbs sampling. Effects of sex, year-month of birth, age of the dog at screening and experience of the x-raying veterinarian were assigned flat priors; kennel and animal genetic effects were given Gaussian prior distributions. Marginal posterior medians (SD) of heritabilities for HD, SP and AA were 0.20 (0.03), 0.38 (0.04) and 0.25 (0.07) respectively. The genetic correlations between these traits were 0.18, for HD and SP, -0.24 for HD and AA and -0.05 for SP and AA. These estimates indicate that breeding programs aimed to reduce prevalence of skeletal and cardiac diseases are feasible, provided that a regular screening program of Boxer dogs is performed. Regarding the effect of inbreeding, slight detrimental effects have been detected for the aforementioned traits.