Buy Photo

Felix Adamo/ The Californian

Columnist Sherry Davis.

Are mixed-breed dogs healthier than purebred dogs? That's been a long-held belief of many people and part of the reason for the increased popularity of "designer dogs" and their inflated prices.

But according to a five-year study at the University of California, Davis, mixed breeds don't automatically have an advantage when it comes to genetic disorders.

The study reviewed the records of 90,000 purebred and mixed-breed dogs, with 27,254 of those dogs having at least one of 24 genetic disorders such as various cancers, heart disease, endocrine system dysfunction, orthopedic conditions, allergies, bloat, cataracts, eye lens problems, epilepsy and liver disease.

The results of the study, published in the June 1 Journal of the American Veterinary Medical Association, showed the prevalence of 13 of the 24 genetic disorders about the same for purebreds and mixed breeds; 10 conditions were found more frequently among purebreds; and one disorder was more common in mixed breeds.

The study data indicates that although purebred dogs, which have developed from similar lineage, share gene mutations and are prone to certain inherited disorders due to common ancestors, disorders such as hip dysplasia, tumor-causing cancers and hypertrophic cardiomyopathy seem to originate from well-established gene mutations that have spread throughout the dog population and occur in mixed breeds as well as purebreds.

Oh, and that myth that by crossing two breeds with a genetic predisposition for the same disorder you will eliminate the chances of their progeny developing it? It's just that, a myth.

Addressing column feedback

A recent letter in the Opinion section of the newspaper admonished me in response to my Oct. 5 column, "Troublesome puppy behaviors left unchecked will snowball." The writer accused me of discouraging the owners of a severely aggressive dog from seeking help for the pet.

The author of this letter, apparently a dog trainer, asserted that my reason for doing so was an apparent lack of familiarity with behavior modification and positive reinforcement techniques, and that I was less than genuine in my desire to keep dogs from being surrendered to shelters.

Normally I would shrug off a letter like this by remembering the old dog trainer's adage, which advises that "the only thing two dog trainers agree on is what the third trainer is doing wrong." But on an ethical level, I felt a response was in order.

The letter writer quoted me out of context and apparently missed my point.

"Sometimes I want to take hold of an owner, shake him or her, and demand to know their priorities" was quoted by itself with the assertion that my objective was to demean and embarrass owners for allowing behavior problems to develop.

But with the next line included, "No matter how much you love a dog, if it is aggressive, it has no business being around children," I think my motivation is clear.

This article was not intended to assess or dismiss the trainability of this dog, the methodology needed to teach it or as a recommendation for keeping it or finding it a new home. Nor was it meant as an attack on the owners for any culpability in the development of its problems.

Allowing a dog with a history of snapping and biting free access to children (the owner's or someone else's) is child endangerment.

And not questioning an owner's choice to address long-ignored training issues before that of the immediate priority to protect a child would make me guilty of professional and ethical negligence.

Sherry Davis is a dog trainer/ owner of CSI 4 K9s. Email her at These are her opinions, not necessarily The Californian's.