In defense of the dog


UC Davis research explores genetic effects of purebred versus mixed breed canines

Which is better: a purebred or a mixed breed dog?

Although the choice is that of owner’s, Dr. Thomas Famula, statistician and UC Davis professor of animal science, can help to impartially determine a dog’s genetic makeup which in turn might influence this end decision.

His research focuses on animal genetics ranging anywhere from livestock to topics such as Guide Dogs for the Blind. Since the ongoing debate between purebred and mixed breed dogs centers around the basis of the mating practices and health implications associated with inbreeding, Famula’s research is especially helpful in this field.

“Inbreeding does […] not make animals sick, [as] it’s just a mating strategy. What it does is genetically […] expose disease,” Famula said. “The reason people are against purebreds is because the population’s closed you are mating relatives, increasing the homozygosity [of the genes]. They still have health issues […] but they have that uniformity and that’s what the breed created.”

Some of Famula’s data collection of guide dogs focuses on creating better companions to assist the visually impaired. From this first-hand experience, Famula has been able to see the phenotypic (visual) and genotypic (genetic) effects in the breeding industry, which determine the health and concerns of the individual dog as well as influence the rest of the breed.

“The hope for dogs is that the genetic information will be useful, so that’s why our research is mostly on [if we can] find the genes,” Famula said. “[Right now], for a few genes in a few places, you can do that in dogs. Then, you don’t have to keep track of all the dogs [because] you’ve got DNA.”

As there is no current data set for the entire population of dogs in the United States, the hope is that molecular genetics could, one day, be more accessible in order to determine the health of a future companion.

“With all this world of nanotechnology, if I could take a sample […] and then look at that DNA and [find out] if they have the bad genes for epilepsy or the bad genes for heart disease, that’s something that would help a breeder,” Famula said. “They’ll have some information, but […] for most traits, we’re not there and other traits are never going to be there.

Dr. Anita Oberbauer, chair of the UC Davis animal science department, has worked with Famula on a number of papers concerning the effects of dog breeding. Through her work, she has seen that genetics could drastically improve the outlook for canine health, but emphasizes that the issue is more complex than that.

“If we knew the consequences of every single gene and every single nucleotide alteration, then we could predict the outcome of every genetic combination,” Oberbauer said in an email interview. “There are health improvements that can be done to reduce the incidence of deleterious conditions, [but] one must be mindful to avoid unintended consequences.”

Oberbauer is realistic when it comes to greater accessibility of genetic testing for all dog breeders to preserve the health and outlook for the individual dog.

“Knowledge and a willingness to improve the health of dogs must be applied to improve the overall health of the entire canine population […] and should enable wiser breeding decisions,” Oberbauer said. “Implementing genetic testing must be cost effective, [but] it is unlikely that genetic testing would be incorporated into the random bred dog population.”

In a 2013 study that collected over 27,000 dogs’ health records from the UC Davis Veterinary Medical Teaching Hospital, Oberbauer and Famula were able to statistically determine the probability of specific diseases when comparing all mixed breed dogs directly to all purebreds. According to a probability ratio of certain diseases in purebreds over mixes, purebreds were more likely to contract specific cardiac and orthopedic diseases, though 13 of the 24 disorders had no significant difference.

“The general belief [is that] purebreds are sick and mixed animals are healthier –– it was an everyday assumption, but [there was] never any data on it,” Famula said. “[These results don’t] mean mixes are totally healthy. Mixes got [aortic stenosis] too, but [they] are three times more likely [to contract it] if [they’re] purebred. The mixes were more likely to be hit by a car and […] to have ruptured crucial ligaments.”

Sergeant Michael Nevis, supervisor of Animal Services at the Yolo County Animal Shelter, discussed the different types of canines seen in shelters in the Davis area.

“Most animals that come here are mixed breed type animals. Very seldom do we get a purebred type of animal ––  [but] unfortunately they go a lot faster than a lot of the others,” Nevis said. “Part of the reason is that […] you spend quite a bit of money to get that purebred animal, so you have to take care of it more because you have more invested in it.”

Famula understands the potential moral concerns one may have in adopting a purebred over a mixed breed dog, but just like each individual dog’s health is dealt with on a case by case basis, no assumptions can be made about a human’s choice in companion.

“Breed is a human invention, created by people [and] maintained by people. People’s egos are wrapped up a lot of the time in the pets they own; that’s a moral quandary for other people to discuss, not animal breeders,” Famula said. “There’s no perfect animal that doesn’t have any disease, that’s ridiculous. There’s no perfect person, there’s no perfect animal.”
Written by Emilie DeFazio