The short legs of a dachshund, wrinkled face of a pug, and spotted coat of a Dalmatian are some of the distinctive dog breeds. Genetics that give various breeds their particular attributes are often the result of inbreeding.
A team of researchers led by the University of California, Davis have shown that the majority of canine breeds are highly inbred, which can lead to an increase in disease and health care costs.
Bannasch said that inbreeding seems to matter to health. Previous studies have shown that small dogs live longer than large dogs, but no one had previously reported on morbidity or the presence of disease. The study showed that if dogs are of smaller size and not inbred, they are more healthy than larger dogs.
Health is affected by inbreeding.
Sharing the same genetic material with a full sibling was the equivalent of 25% inbreeding, based on genetic analysis of 227 breeds. These levels are considered to be safe for both humans and wild animal populations. In humans, high levels of inbreeding have been associated with increased prevalence of diseases.
The relevance of high inbreeding in dogs to their health is highlighted by the data from other species and strong breed predispositions to complex diseases.
The researchers collaborated with Wisdom Health Genetics to get the largest sample size possible for analysis. Wisdom Health's database is the largest in the world, with over 50,000 dogs in it.
Some breeds are more inbred.
What makes a dog different from others? Bannasch said that it's often a combination of a small founding population followed by strong selection for particular traits in a breed. She has always been interested in the population structure of some of the breeds, but she became more interested in the Danes-Swedish farm dog several years ago. She fell in love with them and imported one from Sweden.
Bannasch discovered that the Danes and Swedes have a low level of inbreeding because they are bred for function rather than for looks. The farm dog is one of the healthiest breeds according to the insurance health data on the breeds collected from Agria Insurance Sweden and hosted online by the International Partnership for Dogs.
There was a significant difference in morbidity between brachycephalic and non-brachycephalic breeds. The researchers removed brachycephalic breeds from the final analysis on effects of inbreeding on health.
Preserving the genetics.
Bannasch isn't sure if there is a way out of inbred breeds. People know that creating matches is not always the best idea. The inbreeding calculator doesn't go back far enough in a dog's genetic line, and that method doesn't improve overall high levels of population inbreeding.
She said that there are other measures that can be taken to preserve the genetic diversity and health of a breed. Careful management of breeding populations to avoid additional loss of existing genetic diversity is one of the things they include.
If outcrosses are to increase genetic diversity and reduce inbreeding, they need to be done with care, Bannasch said. Every effort should be made to maintain the genetic diversity in the few breeds with low inbreeding levels.
Other authors at UC Davis include Kevin Batcher, Sara Thomasy, and Robert Rebhun. Contributors from Wisdom Health Genetics include some people.
The work was supported by two funds.
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The materials were provided by the University of California - Davis. The original was written by Trina Wood. Content can be edited for style and length.
