Inbred dog breeds share as much genetic material as siblings
Dog breeds are often recognized for their distinctive features – the short legs of a Dachshund, the wrinkled face of a pug, the spotted coat of a Dalmatian. Unfortunately, the genetics that give various breeds their particular attributes are often the result of inbreeding.
In a recent study Posted in Canine medicine and genetics, an international team of researchers led by the University of California at Davis, veterinary geneticist Danika Bannasch show that the majority of dog breeds are highly inbred, which contributes to increased disease and health care costs throughout of their life.
âIt’s amazing how much inbreeding seems to matter for health,â Bannasch said. âWhile 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 if dogs are small in size and not inbred, they are much healthier than larger dogs with high inbreeding.
Inbreeding affects health
The average inbreeding based on genetic analysis of 227 breeds was close to 25%, which is the equivalent of sharing the same genetic material with a full sibling. These are levels considered to be well above what would be safe for humans or wildlife populations. In humans, high levels of inbreeding (3-6%) have been associated with an 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, highlights the relevance of high inbreeding in dogs to their health,” Bannasch said. , who also holds the Maxine Adler Chair in Genetics at UC Davis School of Veterinary Medicine
The researchers partnered with Wisdom Health Genetics, a world leader in companion animal genetics, to obtain the largest possible sample size for analysis. The Wisdom Health Database is the world’s largest canine DNA database, helping researchers collect data on 49,378 dogs of 227 breeds, mostly from European sources.
Some more inbred breeds
So what makes one dog breed more inbred than others? Bannasch explained that this is often a combination of a small founding population followed by strong selection for particular traits of a breed – often based on appearance rather than purpose. While she has always been interested in the population structure of some of these breeds, she was particularly interested in the Danish-Swedish farm dog several years ago. She fell in love with their compact size, disposition and intelligence, and ended up importing one from Sweden.
Bannasch discovered that Danish-Swedish farm dogs have a low level of inbreeding based on their history of a relatively large founder population of 200 and being bred for function, rather than strong artificial selection for l ‘appearance. And according to breed health insurance 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 revealed a significant difference in morbidity between brachycephalic races (short skull and muzzle) and non-brachycephalic races. While this finding was not unexpected, the researchers removed the brachycephalic races from the final analysis of the health effects of inbreeding.
Preserving genetic diversity
Ultimately, Bannasch said she wasn’t sure there was a way out of inbred races. People have recognized that creating matches based solely on pedigrees is misleading. Inbreeding calculators do not go far enough into a dog’s genetic lineage, and this method does not improve the overall high levels of inbreeding in the population.
There are other steps that can be taken to preserve the genetic diversity and health of a breed, she said. They include careful management of breeding populations to avoid further loss of existing genetic diversity, through education of breeders and monitoring of inbreeding levels enabled by direct genotyping technologies.
Crossbreeds are proposed or have already been made for certain breeds and conditions as a measure to increase genetic diversity, but care must be taken to determine whether these will effectively increase overall racial diversity and therefore reduce inbreeding, Bannasch said. In particular, in the few breeds with a low level of inbreeding, everything must be done to maintain the genetic diversity present.
Bannasch D, Famula T, Donner J, et al. The effect of inbreeding, body size and morphology on the health of dog breeds. Canine medicine and genetics. 2021; 8 (1): 12. do I:10.1186 / s40575-021-00111-4
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