New US research shows that inbreeding depression, the result of breeding closely-related individuals, reduces litter sizes in purebred golden retrievers.
Conducted by Morris Animal Foundation research partners at Embark Veterinary Inc. in Boston—and published in Mammalian Genome—the study is one of the first to examine genetic measures of inbreeding in domestic dogs rather than using pedigree-based estimates.
“This scientifically proves something we’ve known anecdotally for a few years; that fecundity, or the measure of how successfully a dog can reproduce, is threatened by inbreeding,” veterinary geneticist Dr Erin Chu said.
“Breeders need to ensure that the dogs they choose to mate maintain diversity in their lineages to preserve healthy and successful breeds.”
For the study, the team examined DNA and phenotype data from 93 female golden retrievers. All the dams were reproductively intact and had been bred at least once.
In addition to the dams’ basic biological information, the team analysed data that captured every aspect relating to the dams’ reproduction. The researchers evaluated the associations of all these data points against a genomic coefficient of inbreeding, which measures how closely related a dam and sire are.
The team discovered that the degree to which a dog was inbred influenced the number of puppies it birthed. They found that, on average, a dam that is 10 per cent more inbred than another will produce one less puppy per litter.