Many people believe that mixed breed dogs are healthier than their purebred counterparts. An understanding of what makes for a healthy dog suggests this is an over generalization. We know that, while genetics are very important, there are many other factors that also play a role. Using our knowledge of epigenetics (see HDB post The Only Difference is What Their Mother Ate!), we have a better understanding how things such as nutrition, vaccines, toxin exposure, and joyful living, including exercise, can alter genetic expression. The result is a dog that is either more healthy or less healthy than the genes he was born with might imply.
While we may be able to modify their expression, is there any evidence that purebred dogs are at higher risk for genetic disorders? In a study recently published in the Journal of the American Veterinary Medical Association (http://avmajournals.avma.org/doi/abs/10.2460/javma.242.11.1549), 27,254 dogs with an inherited disorder were examined in a case-control study. There was no difference between mixed and purebred dogs in expression of 13 of 24 common genetic disorders studied (eg, hip dysplasia, hypo- and hyperadrenocorticism, cancers, lens luxation, and patellar luxation). Ten genetic disorders were more common in purebred dogs and one was more common in mixed-breed dogs. While these data are interesting, keep in mind that analysis of a different list of genetic disorders would have yielded different results.
Many believe the ultimate measure of wellness is longevity. There is no good evidence that mixed breed dogs live longer than purebred dogs of similar size. In my research, I found that the oldest living dog on record was Bluey, an Australian cattle dog. Bluey, who worked with cattle and sheep for nearly 20 years, lived to the age of 29 years 5 months!
So, what is the bottom line? In many ways, the health of your dog lies as much in your hands as in the genes he was born with. Pet ownership is a big responsibility. Our goal is to provide you with the information you need to make the best decisions you can for the health of your dog, whether he is a purebred or mixed breed dog.