In commemoration of National Mutt Day, I am exploring the notion that mixed breed dogs have health advantages over pure breeds.

What exactly makes a mutt? "Mutt" is a term typically referring to dogs, but does not necessarily exclude animal counterparts of other species. The term mutt is often used in a derogatory fashion, but it should be perceived in a more positive light. A mutt is merely a living being having a mix of known or unknown genetics. One can even consider most humans to be mutts due to our various genealogical lineages. Heck, I'm a French, Irish, and Lithuanian mutt.

Not all canines fit into the mutt category, as some dogs have specific genetic lineage that is traceable through generations and are thereby known as pure breeds. The American Kennel Club (AKC) defines purebred as a "dog whose sire and dam belong to the same breed and who are themselves of unmixed descent since recognition of the breed."

As a practicing veterinarian I am aware of the commonly held perspective that mutts are healthier than pure breed dogs. There are some aspects of this statement that I agree with and others with which I disagree.

From a clinical perspective, what may make a mutt healthier is the general lack of awareness of specific illnesses that develop based on their genetics. Veterinarians can cite specific examples of pure breed dogs and rattle off a list of breed specific diseases; plus one for the mutts.

Veterinarians can never certify that a mixed breed dog will completely lack the potential for developing a genetically correlated disease. We can only speculate that a mutt may have a reduced likelihood as compared to a particular pure breed; minus one half for the mutts.

An example of this mixed versus pure breed phenomena is hip dysplasia (HD), one of the most common canine orthopedic abnormalities. HD (AKA Coxofemoral subluxation) is a developmental malformation of the hip joint that highly correlates with the genetics of many large dogs. HD is an undesirable trait, as it increases the likelihood that a dog will suffer from painful osteoarthritis during its lifetime.

Acquiring a dog from a reputable breeder who uses Penn HIP or Orthopedic Foundation for Animals (OFA) techniques to evaluate the sire and dam’s hip health can reduce the likelihood that the offspring of normal parents will develop hip dysplasia.

Breeds of dogs that are prone to hip dysplasia include (but are not limited to) the Golden and Labrador Retriever, Rottweiler, and German Shepherd Dog. Not every dog within these pedigrees has HD, yet plenty of mixes of these and other breeds do.

As compared to a dog’s breed, a more realistic determining factor of the likelihood of developing HD is physical size. Generally, large dogs (roughly > 50 lbs) are more likely to develop hip dysplasia than small dogs (say < 20 lbs), regardless of being a pure or mixed breed.

Additional factors that play a role in a dog’s development of HD are:

• Fast rate of weight gain
• Obesity (see Pet Obesity: Health Implications, Recognition, and Weight Management)
• Elevated protein, calcium, and other nutritional factors
• Traumatic joint injury

Although acquiring a dog of prime and known genetic stock may reduce the likelihood that a disease like HD will develop, the overall picture of health and wellness is multifactorial. Both pure and mixed breeds have the same potential to develop illness secondary to toxic exposure or infection. Additionally, getting hit by car, enduring a dog fight, falling from heights, and other traumas have no mixed versus pure breed discriminatory pattern.

I am all for adopting a pet, provided you have adequate time, financial resources, and have made this decision in a well thought out manner. Organizations like PetFinder are leading the way in the on-line adoptive realm and are currently striving to place nearly 200,000 dogs into homes.

Interestingly, PetFinder lists the available canines by known or suspected breed categories. A disclaimer reads:

Breed Note: Many of these pets are mixes. In these cases, the breed listed is the one that best matches their looks and personality. Also, some of the pets presumed to be mixes may be purebred.

Perhaps claiming a dog is a particular breed makes it more adoptable after all.

Truly, I hope your mutt, pure breed dog, cat, or other companion animal lives many years having a great quality of life. Providing the best pet parenting possible, along with some good fortune, can help make this goal a reality.

Dr. Patrick Mahaney

This photo of one of my favorite mutts comes courtesy of Oregon Artist Donald Brown. The dog's name is "Sergio"