"Health of purebred vs mixed breed dogs: the actual data"
I wrote this last year, but it clearly needs to get out more because every few days I hear somebody proclaim that "Purebred dogs are just as healthy as mixed breed dogs!"
The latest is in this month's Canine Chronicle, in an argument against the breeding of "designer dogs". The designer dog thing is beside the point here, but what is really troubling is the amount of misinformation that is declared to be scientific fact, of which the mixed vs purebred thing is just one example.
The bottom line is that we can't reduce the alarming prevalence of genetic disorders in purebred dogs if breeders don't know even the most basic things about genetics. If we can't do better than this, I despair for the future of the purebred dog.
How many incorrect statements presented as scientific "facts" in this article can you find? (Hint: I've written about many of them in my blogs on the ICB website, and just scanning the list of titles should turn up a few.)
The Canine Chronicle article:
"Raising the alarm on designer breeds"
Here's the note I sent to Tom Grabe, the Chronicle's editor:
I was so pleased to see Peri Norman's article about the need to preserve the genetic diversity in our purebred dogs for the same reasons that there are now global efforts to protect the "heritage" livestock breeds.
But I'm dismayed to see in this month's issue the piece by Attila Márton about designer dogs that is full of statements that are demonstrably false. Anybody who survived an undergraduate (or even high school) biology class will have learned about dominant and recessive alleles and should be able to explain why breeding related dogs together will increases the risk of producing genetic disorders, because related dogs are likely to share the same mutations. Similarly, breeding unrelated dogs, such as two different breeds, will reduce the risk of genetic disorders.
Not only does that make perfect sense, but it is borne out in the studies the author claims don't exist. The so-called "Davis" study was widely claimed amongst the dog show folks to have proven that purebred dogs are just as healthy as mixed breeds. In fact, it clearly shows just the opposite. Mixed breed dogs are more likely to have three problems: patent ductus arteriosis (an anatomical condition), ruptured cruciate ligament, or injury from getting hit by a car. For all of the other conditions reported in the study, purebreds were worse off, as I have summarized here: Health of purebred vs mixed breed dogs: the actual data.
I won't go through all of the other false claims in that article, but I would point you to my discussions about hybrid vigor in dogs (The myth of hybrid vigor in dogs...is a myth), about why DNA tests will not solve the problem of inherited disorders in dogs (Why DNA tests won't make dogs healthier), about why recessive mutations have become such a problem (Why all the fuss about inbreeding? (Or "Why are there so many genetic disorders in dogs?"), and about why it's impossible for a breeder to "know what's in my lines" (The fiction of "knowing your lines"). I would also point you towards Three key strategies to reduce genetic disorders in dogs and Ian Sneath's commentary about it (The sins of the father are laid upon his children).
I've put down the camera and have spent the last three years doing the much more important work of trying to educate breeders about the genetics they MUST understand if we are to reduce the burden of genetic disorders in purebred dogs. To solve this problem, breeders will have to get the science right, whether they believe it or not. I urge you to use your platform to help clear the facts from the rubble by insisting that those writing about the genetics of breeding know what they're talking about.
With my best regards,