Monday, November 22, 2010

The Importance of Genetic Diversity

Purebred dog breeding is a study in genetic restriction.  The idea being, each created breed is to be held to a unifying standard of type (i.e. physical appearance), personality, and specific working ability.  When a person wants a rough collie, they have a reason for choosing a rough collie over a border collie, australian shepherd, or other herding dog.  Each breed has specifics that make them unique and worth preserving.

However, by restricting breeding to a specific gene pool, you have the elements of disaster at your fingertips if breeding isn't planned out appropriately.  When you look at the astonishing number of genetic health problems associated with purebred dogs today, small gene pools, bottle necking, and inbreeding are to blame.  When you restrict breeding to "enhance type" you're obviously going to come across bizarre mutations that can be detrimental down the road.  There's a reason we don't marry our cousins.

Unfortunately, with breeds that were established and over bred in a time when we didn't understand such things in genetics, problems are cropping up that quite possibly won't ever be able to be fixed.  Even with reputable breeders testing for and breeding against problems common in their breed, with some issues (like heart problems in cavalier king charles spaniels) it's just a band-aid that will never really get rid of the problem all together.  You can go to such breeders to reduce the risk of getting an unhealthy pet, but in the end, statistically speaking, the breed would still be doomed.
Virtually all cavaliers will be affected by Mitral Valve Disease by age 10.

The only solution for breeds that are this far gone is to bring in new genetics by outcrossing from different breeds.  This creates a panic with some breeders who are too concerned with "tradition" and "purity" to take their blinders off and see the benefits of outcrossing.  It's already been proven that with careful, insightful breeding, and a fantastic eye for dogs, you can outcross with a different breed and produce puppies in a few generations that will breed true to the original standard.  Take the Dalmation/Pointer outcross as example:

"The Dalmatian Backcross Project commenced in 1973 with the original outcross of an AKC registered Champion Pointer sire CH Shandown's Rapid Transit bred to an AKC registered Dalmatian dam Lady Godiva Dr. Robert Schaible conducted the breeding in an effort to address the Dalmatian fixed genetic defect that affects uric acid metabolism and that may lead to increased urinary uric acid, urate crystals, urinary bladder aggregate formation, stones, urinary tract obstruction and even death."

Despite the fact that the products of this outcross are dogs that are indistinguishable from purebred dalmations, breeders are still fighting their recognition into the AKC.  These dogs, and future outcrossing, would help save a breed that is on a downward slope into oblivion, but instead people fight and cling to a past that has failed the breed miserably.

Obviously, not all breeds are so far gone that outcrossing to other breeds is necessary.  Some breeds still have only minor issues that can be avoided through careful observation of lines and testing of the breeding pair.  What can we do now, though, to avoid the mistakes of the past?  Knowing what we now know about genetics, what can we do to preserve breeds for the future?

The answer is simple: stop inbreeding!  We know that by breeding close dogs we limit an already small gene pool.  Despite the fact that doing so supposedly "locks in" positive traits in a line, it's undeniable that it causes a major blow to the offspring in the genetics department.  We've learned that you want as few common ancestors in a dog's pedigree as possible and close inbreeding cuts that diversity in half.  Even without breeding dogs that are "related" in the sense that they are father/daughter, grandparent/grandchild, cousins, etc, we've found that by looking back in a pedigree, a loss of diverse ancestry causes major genetic issues down the road.  In breeds with rampant health issues, it's a certainty that if you look at the breed's history you will find areas of bottlenecking, often caused by popular stud dogs who may be ideal and high winning, but through over breeding show up in virtually every pedigreed dog.

We need to take a look at the proof these statistics have shown us and make a unanimous decision that when breeding, genetic diversity and health should come first, even before the ideal set forth by the standard.  Breeding is an art that takes time.  The idea is to create a line and improve upon it over the course of numerous generations.  There is no reason to take shortcuts on the road to this perfection if the cost is detrimental health issues down the road.  Breeders need to stop being so short sighted with breeding "perfect" show dogs or sport dogs and do something valuable for the breed as a whole.  It might take a hell of a lot longer, but it will be worth it in the end.


  1. I'm wondering if you've been keeping up with Jemima Harrison's blog:

    I didn't think much of her biography, but her blogging is informative, and she sounds right up your alley.

  2. haha Shows how much attention I pay to this! I actually JUST saw that yesterday, through Pet Island. I totally agree that the documentary was pretty bias, but yeah, the information is still sound. Like everything, though, you just can't take things to extremes.