Mutts and Purebreds: Is One Healthier Than the Other?

• Can We "Design" Healthier Dogs?
• What Factors May Determine Health in Breeding?
• What Do Research and Experience Tell Us?
• Which Have Better Health Chances?

Can We “Design” Healthier Dogs?

Once upon a time, there were two types of dogs: purebred, carefully (sometimes not so carefully) bred for specific traits to improve what kennel clubs established as “breed standards”; and mutts, dogs of questionable parentage that were usually accidentally conceived.

The result was that purebred dogs were often bred from a small gene pool, which had the unintended result of inherited problems—like congenital heart disease or hip issues—becoming rampant in the breed. Conversely, since mutts were bred from a much more diverse group, it was thought that they escaped the fate of these “inbred” puppies. Thus, a great debate was born.

Today, we have a third type of dog: “designer dogs,” or dogs that are intentionally crossbred. The theory is that crossing two (or more) purebred dogs will create a healthier dog because you are again enlarging the gene pool. But here’s the conundrum: Are designer dogs mutts? Technically speaking, yes, and calling them such is insulting to some people, as the term has come to have a negative connotation.

In the truest sense of the word, however, a “mutt” is a dog with parents that are not of the same breed, usually bred without intention. And that’s why designer dog breeders take issue with the term. These breeders are, with great intent, creating mixed breeds to breed dogs with specific traits, just as purebred breeders are.

Breeders can love a certain breed but are unable to own a dog of that breed because of allergy issues. They thus have the goal of breeding dogs that retain some of the personality traits of the original breed, while also trying to make the offspring hypoallergenic. Some argue that they are in the process of creating a healthier breed. But are they?

What Factors May Determine Health in Breeding?

When you cross two breeds, the hope is that you cut in half the chances of the puppies inheriting a genetic disorder. In reality, though, the health issues could be doubled. Poodles and Labradors share some of the same inherited disease risks, so breeding them together can result in some affected labradoodle puppies if the parents both carry, say, the hip dysplasia or epilepsy gene.

Dr. Mark Scribano, Chief of Staff and veterinarian at Northeast Animal Hospital, observes that ‘historically, it appears that when any breed gains popularity and becomes hugely desired, then breeding becomes relatively less discriminate to keep up with the demand. Unethical breeders will use dogs with heritable defects with the sole intent to produce volumes of puppies.’ This adds to purebreds having the reputation of poorer health than mutts.

Still, reputable breeders of both purebred and designer dogs will argue that, due to the easy access to genetic testing, they can exclude dogs from their breeding programs that carry genetic diseases and, therefore, can theoretically guarantee a healthy dog.

And that’s where things get hairy—or furry—because there are so many purebred dogs that live long, healthy lives and others that inherit diseases. At the same time, there are also so many mutts that live long, healthy lives and others that inherit diseases. Yet some vets say, based on the number of dogs they treat, that mutts are more robust and are seen less often for inherited disorders.

What Do Research and Experience Tell Us?

Dr. Ginger Benham, a veterinarian at Northeast Animal Hospital, states that based primarily on her 15-plus years of experience, “Brachycephalic syndrome is a very severe congenital disorder that can cause a range of issues throughout a dog’s life. I have seen that condition less than a handful of times in mutts, but have seen it to some degree in every single pug, French bulldog, and English bulldog that I have treated.”

Dr. Benham goes on to say, “Another similar example would be King Charles Cavalier Spaniels and mitral valve endocardiosis. Endocardiosis, or degeneration of the heart valves, is the most common form of heart disease in dogs, especially small and medium dogs of any breed (or mixed breeds). However, King Charles Cavalier Spaniels are virtually guaranteed to get this disease by 8-10 years of age.

“There are also instances of diseases that are found almost exclusively in purebred dogs. For example, von Willebrand’s disease in Doberman pinschers. Dilated Cardiomyopathy used to fall into this category as well, where it was seen almost exclusively in Dobermans, cocker spaniels, golden retrievers, and a few other purebred dogs. That has changed since we have seen so many cases of dilated cardiomyopathy related to food, specifically grain-free and boutique diets.”

Researchers attempted to study the veterinary records of over 90,000 purebred and mixed-breed dogs from the University of California–Davis in 2013. Bellumori and his group of researchers found that, out of 24 genetic disorders found in over 27,000 dogs, 10 of them were found significantly more often in purebred dogs.

Ruptured cranial cruciate ligaments were found more often in mixed-breed dogs. Regarding the other 13 genetic disorders, researchers did not find that there was a great deal of difference between the two groups of dogs. So, they concluded that purebreds aren’t always unhealthier. (See study notes below.)

Which Have Better Health Chances?

Many dog experts disagree with this conclusion and even the test subjects. After all, it’s nearly impossible to compare apples to…even other apples. Where were the apples grown? Did they get the same level of care in their fertilization, water, sunlight, temperature, pruning, and parasite prevention? Unless the apples were grown under laboratory conditions, there will always be something that can skew the results.

The same is true with dogs. Were their parents genetically healthy? Are they overweight, which can contribute to some disorders such as intervertebral disk disease? What kind of care did the dogs receive? Some say purebreds are more likely to receive veterinary care and thus have genetic diseases diagnosed in greater quantities.

If that characterization were true, could it be why some vets typically see healthier—albeit fewer—mutts compared to purebreds? We can speak from our own experience that we have a large population of mixed-breed patients that receive excellent care from their pet parents, so again, it’s hard to say who is correct.

What we can determine in this great debate is that mixed breed and purebred dogs all need love and a home to call their own. The choice of a purebred or mixed-breed dog is up to each individual to decide. Whatever your choice, whether a mutt or purebred, we are here for you and your dog to help ensure they live the longest, healthiest, happiest life possible.

Northeast Animal Hospital and Downtown St. Pete Vet Clinic are sister practices located in sunny St. Petersburg, Florida. We are devoted to helping pet owners connect with their pets while educating them on topics that will help keep their pets happy and healthy. If you are local to St. Pete and its surrounding areas and have any questions, please don’t hesitate to contact us. If you’ve found us through a web search, we hope we’ve helped answer your question on this subject. If you reside beyond the Tampa Bay area we recommend you contact your local veterinarian for any further needed assistance.

Data Source

• Bellumori TP, TR Famula, DL Bannasch, JM Belanger, & AM Oberbauer  2013 Prevalence of inherited disorders among mixed-breed and purebred dogs: 27,254 cases (1995-2010).  J Am Vet Med Assoc 242: 1549-1555.

Affiliation

• Department of Animal Science, College of Agricultural and Environmental Sciences, University of California-Davis, Davis, CA 95616, USA.
• PMID: 23683021
• DOI: 10.2460/javma.242.11.1549

Abstract

Objective: To determine the proportion of mixed-breed and purebred dogs with common genetic disorders.

Design: Case-control study.

Animals: 27,254 dogs with an inherited disorder.

Procedures: Electronic medical records were reviewed for 24 genetic disorders: hemangiosarcoma, lymphoma, mast cell tumor, osteosarcoma, aortic stenosis, dilated cardiomyopathy, hypertrophic cardiomyopathy, mitral valve dysplasia, patent ductus arteriosus, ventricular septal defect, hyperadrenocorticism, hypoadrenocorticism, hypothyroidism, elbow dysplasia, hip dysplasia, intervertebral disk disease, patellar luxation, ruptured cranial cruciate ligament, atopy or allergic dermatitis, bloat, cataracts, epilepsy, lens luxation, and portosystemic shunt. For each disorder, healthy controls matched for age, body weight, and sex to each affected dog were identified.

Results: Genetic disorders differed in expression. No differences in the expression of 13 genetic disorders were detected between purebred dogs and mixed-breed dogs (ie, hip dysplasia, hypo- and hyperadrenocorticism, cancers, lens luxation, and patellar luxation). Purebred dogs were more likely to have 10 genetic disorders, including dilated cardiomyopathy, elbow dysplasia, cataracts, and hypothyroidism. Mixed-breed dogs had a greater probability of ruptured cranial cruciate ligament.

Conclusions and clinical relevance: The prevalence of genetic disorders in both populations was related to the specific disorder. Recently derived breeds or those from similar lineages appeared to be more susceptible to certain disorders that affect all closely related purebred dogs, whereas disorders with equal prevalence in the 2 populations suggested that those disorders represented more ancient mutations that are widely spread through the dog population. Results provided insight into how breeding practices may reduce the prevalence of a disorder.