Most Dog Breeds Are Super Inbred, Study Finds

English Bulldogs are especially prone to breathing and other health issues due to the unique shape of their body and face created by reproduction.

English Bulldogs are especially prone to breathing and other health issues due to the unique shape of their body and face created by reproduction.
Photo: Jacob King / PA Wire (PA)

New research seems to confirm the idea that many of our cutest purebred puppies are also overwhelmed by their genetics. The study determined that most dog breeds have high levels of inbreeding. Additionally, this inbreeding can contribute to various health issues and expensive vet bills over time, especially for large dogs.

It is certainly not surprising that some dog breeds do not have robust health.— Often the result of long-term breeding programs that use closely related parents to select for the most valued traits in a breed. Brachycephalic dogs like the pug or the bulldog are well known for their increasingly squashed faces, for example, a characteristic which predisposes them to breathing problems (not to mention their other issues). This new study, a collaboration between veterinary researchers from California and Finland, set out to take a broader view, hoping to get some idea of ​​the impact of inbreeding on the pedigree dog population in general. .

To do this, they turned to a genetic database made up of the results of commercial DNA tests of nearly 50,000 dogs, encompassing 227 breeds in total. Then, they analyzed the average genetic similarity of dogs within a breed in order to estimate their level of inbreeding on a percentage scale of 1 to 100. To further verify their calculations, they compared their results to data from previous studies that looked at smaller breed groups. .

Overall, they estimated the average level of inbreeding among these breeds to be around 25%, which is roughly the degree of genetic similarity you would see between two siblings. But while it’s good for two members of a family to be this close, it doesn’t bode well for a population of animals that depend on genetic diversity, as most do. At levels much lower than in humans (around 3% to 6%, according to the authors), you may start to see a higher risk of inherited disorders or other conditions influenced by genes, like cancer.

“Data from other species, combined with the breed’s strong predispositions to complex diseases like cancer and autoimmune diseases, highlights the relevance of high inbreeding in dogs to their health,” said study author Danika Bannasch, veterinary geneticist at the University of California, Davis, in a declaration of the University.

Bannasch and his team took their research one step further, crossing their findings with data from a pet insurance database, using insurance claims for non-routine vet visits as dog health indicator. Dog breeds with higher inbreeding levels were more likely to need additional veterinary care than others, they found, although factors like size also played a key role. Brachycephalic races were also less healthy than non-brachycephalic average dogs.

“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 if dogs are small and not inbred, they are much healthier than larger dogs with high inbreeding, ”said Bannasch.

The team’s findings were published in Canine Medicine and Genetics.

Bannasch and his team found dog breeds that were much less inbred, like the Danish-Swedish farm dogs. These dogs are probably best protected due to a large established population and because they are always bred for various jobs, not just for their appearance. And not all of the high inbreeding breeds appeared to be more unhealthy as a result.

But the authors say “careful management of breeding populations” is needed to preserve the existing genetic diversity of all of these dogs, both in educating breeders and in using genetic screening to keep tabs on them. inbreeding levels. Some breeders have started to crossing their dogs (breeding with non-pedigree dogs) in the hopes of improving the genetic health of purebred populations, but the authors warn that even these efforts need to be carefully monitored to ensure that they will truly improve diversity.

While there has been some recognition of the problem, dog breeding groups and organizations have been hesitant to admit many flaws with the current state of affairs. In response, some veterinary groups have even started to plead with people not to buy popular breeds like the pug, while at least one country, the Netherlands, has passed strict laws on breeding brachycephalic dogs.


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