Monday, April 02, 2007

Oooo. Inbreeding. Sccaarrryy....

I'm having a discussion with someone on a list which shall not be named (not a Min Pin or Doberman list). A nice person, and I even considered getting a puppy from her at some point. But she sure has a myopic view about breeding.

This person has bought into the religion of "inbreeding is evil." According to these people, inbreeding should be avoided at all costs, all dog breeding should be based on inbreeding coefficients, and only by outcrossing can we avoid breed extinction through inbreeding depression. This theory, popularized in part by the late John Armstrong, blames all of the woes of the purebred dog world on those oh-so-shortsighted breeders who dared to breed close relatives, thus bringing bad recessives to the front and "ruining" breeds.

I've read the information, and in fact have been a member of the canine genetics email list for years, including several years before John Armstrong died, when there was debate between several big-name people, including author Don McCaig (IMO he's a far better author than geneticist). In those days the list was high traffic and the debate hot. After Dr. Armstrong's death the list went pretty much dead and though it still exists, it has very few messages.

In spite of it all, I have never been convinced that inbreeding is bad. Certainly inbreeding has risks. And by inbreeding I mean what most breeders call linebreeding (which geneticists call inbreeding). I think these days very few people do brother/sister sire/daughter dam/son breedings.

The question is, is inbreeding the ruination of a breed? No. How can it be when we have evidence of very inbred breeds who do well, like Portuguese Water Dogs?

Does inbreeding cause inbreeding depression and eventual breed extinction? No...otherwise how do you explain Greyhounds and Salukis, in existance for thousands of years, relatively unchanged, and relatively hardy and healthy? For that matter the Min Pin, a very old breed, is pretty darn healthy and hardy.

Does inbreeding make a breed more susceptible to genetic disease? According to George Padgett (foremost authority on genetic disease in dogs), the breed with the most known genetic diseases is the Cocker Spaniel, with 52 different genetic diseases. But this is drawfed by the mixed breed, with the potential for over 120 different genetic diseases.

Is homozygosity bad? It can be. But it isn't always. Homozygosity can increase the chance for expression of some genetic diseases, but insulates from infiltration of others. If you have a homozygous population that has an extremely low incidence of hip dysplasia, don't you want to keep it that way?

Is outcrossing a solution? IMO no. Outcrossing to what? Dogs are an artificial construct. They've been bred selectively by humans for thousands (some say 100s of thousands) of years. They are a homozygous population. Which is why they are so extremely useful in researching human diseases. It's far easier to find a dog model than a human model because dogs are so darn homozygous. Cross breeding between breeds only provides hybrid vigor protection to the first (F1) generation, and then only for diseases both parent breeds don't share. So breeding a Yorkie to a Min Pin wouldn't do a thing to prevent Legg-Calve-Perthes. And within a certain breed there really, honestly is no such thing as an "outcross" unless you have a pariah or feral population somewhere that has been isolated from the main population for some time.

Such is the case in Basenjis, where the parent club has been able to go to Africa and find some native dogs and thus battle Fanconi Syndrome. Unfortunately there are no feral populations of Min Pins or Dobermans or German Shepherds.

What ruins breeds are bad breeders. Any breeder who breeds for only one thing--such as a perfect head, or hard grip on a sleeve, great herding ability, or even just genetic health or the least amount of inbreeding in the bloodline is not serving the breed well. Good breeders know you have to look at multiple factors and juggle. It's not easy being a good breeder. You have tons of factors to weigh when making breeding decisions. Being too narrow focused on any one issue will end up doing a disservice to the breed.

As for inbreeding--like it or not, we're all doing it, every time we breed. The question is, how do you make it work for you and not against you?

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