Dog breeds

Most dog breeds are highly inbred, new study finds

In a recent study published in Canine Medicine and Genetics, an international team of researchers led by the University of California, Davis, veterinary geneticist Danika Bannasch shows that the majority of canine breeds are highly inbred, contributing to an increase in diseases and health care costs across their lifetime.

“It’s amazing how important inbreeding seems to be for health,” Bannasch said in a statement. “While previous studies have shown that small dogs live longer than large dogs, no one had previously reported morbidity or the presence of disease. This study found that while dogs are smaller in size and not inbred , they are much healthier than large dogs with large inbreeding.”

The average inbreeding based on genetic analysis of 227 breeds was close to 25% or the equivalent of sharing the same genetic material with a full sibling, according to the study. These are levels considered well above what would be safe for humans or wildlife populations. In humans, high levels of inbreeding (3-6%) have been associated with increased prevalence of complex diseases as well as other conditions.

“Data from other species, combined with strong breed predispositions to complex diseases like cancer and autoimmune diseases, underscore the health relevance of high inbreeding in dogs,” Bannasch said. , who also holds the Maxine Adler Endowed Chair in Genetics at UC Davis. School of Veterinary Medicine, said.

The researchers partnered with Wisdom Health Genetics, which has the largest canine DNA database in the world, to obtain the largest possible sample size for the analysis. The researchers collected data on 49,378 dogs from 227 breeds, mostly from European sources.

Bannasch explained that it’s often a combination of a small founding population followed by strong selection for particular traits in a breed – often based on looks rather than purpose. Unfortunately, the genetics that give different breeds their particular attributes are often the result of inbreeding.

While she has always been interested in the population structure of some of these breeds, she became particularly interested in the Danish-Swedish Farm Dog a few years ago. Bannasch found that Danish-Swedish farm dogs have a low level of inbreeding due to their history of a relatively large founding population of 200, and being bred for function, rather than strong artificial selection for l ‘appearance.

According to breed insurance health data collected from Agria Insurance Sweden and hosted online by the International Partnership for Dogs, the farm dog is one of the healthiest breeds.

The study also found a significant difference in morbidity between brachycephalic breeds (short skull and muzzle, like pugs) and non-brachycephalic breeds. Although this finding is not unexpected, the researchers removed brachycephalic breeds from the final analysis of the effects of inbreeding on health.

Ultimately, Bannasch said she wasn’t sure there was a way out of inbred races. Inbreeding calculators do not go back far enough in a dog’s genetic line, and this method does not improve the overall high levels of inbreeding in the population.

However, there are other steps that can be taken to preserve a breed’s genetic diversity and health, she said. They include careful management of breeding populations to avoid further loss of existing genetic diversity, through training of breeders and monitoring of inbreeding levels enabled by direct genotyping technologies.

Every effort should be made to maintain the genetic diversity present in the few low-inbreeding breeds, the report says.

Other UC Davis authors include Thomas Famula, Kevin Batcher, Noa Safra, Sara Thomasy, and Robert Rebhun. Wisdom Health Genetics contributors include Jonas Donner, Heidi Anderson, and Leena Honkanen.