Analysis of the level of inbreeding and relatedness of Bull Terrier dogs – the popular stud dog effect

Abstract

The aim of the study was to analyze the level of homozygosity of a bull terrier dog population due to its small size, forcing mating in kinship and, possibly, overuse of popular stud dogs. The pedigrees of 107 bull terrier dogs (35 males and 72 females), born in 2008-2016 were used to obtain the inbreeding coefficients for all animals and relatedness coefficients between dogs, between bitches and between bitches and dogs. Pedigrees of bull terriers were also analyzed for occurrence the most common stud dogs. The frequency of occurrence of a popular sire was found according to its position in the pedigree. For the most common stud dog, a list of his sons and their progeny was created. In total about 75% of individuals from the studied population were inbred and their average inbreeding was over 0.04. Almost 95% of bull terriers were related with the average relatedness amounting to over 0.07. The highest value of an individual's inbreeding was almost 0.18, and the highest relationship coefficient was between bitches (over 0.61). There was a popular stud dog in the analyzed population that appeared 113 times in the pedigrees of 107 tested animals and his genes were passed on by his 10 sons as well. It should be noticed that the studied population requires constant monitoring of genetic variability and limiting the overuse of popular stud dogs, which should lead to maintain the variability.