Inbreeding impact on litter size and survival in selected canine breeds

•In dogs, litter size and 2 year survival are traits with relatively low heritability level.•A large part of within-breed inbreeding is related to assortative mating practice.•Litter size is negatively affected by both litter and dam inbreeding.•2 year survival and longevity are negatively affected by inbreeding.•Measures should therefore be taken by canine breed clubs to avoid mating of close relatives.

Data obtained from the French Kennel Club and the Fichier National Canin were used to estimate the effect of inbreeding on average litter size and survival in seven French breeds of dog. Depending on the breed, litter sizes were 3.5-6.3 puppies and longevities were 7.7-12.2 years. Estimated heritabilities were 6.0-10.9% for litter size and 6.1-10.1% for survival at 2 years of age. Regression coefficients indicated a negative effect of inbreeding on both individual survival and litter size. Although the impact of baseline inbreeding within breeds appears to be limited, the improper mating of close relatives will reduce biological fitness through significant reduction of litter size and longevity.