(Photo by Tereza Huclova, provided for the upcoming book by the Kladruber Stud)

This post first appeared on July 22, 2011
Several people have commented about the convex profiles of the Kladrubers and how they are visible even in the foals. I thought I would share this photo since it illustrates the characteristic so well. The extent of the arch varies from horse to horse, but it does seem especially pronounced in the black horses. As someone who grew up around Walking Horses when this type of head was not uncommon, I find it very appealing.

I also received a number of responses about genetic diversity and closed registries, so I thought I would include some links and reference material for those with an interest in the subject.

One book I like to recommend is Bred for Perfection by Margaret Derry.

In the book Derry explores how culture, economics and the (then new) science of genetics shaped the world of stud books and animal breeding. She doesn’t shy away from the less appealing aspects of that history – namely the close association with eugenics and social Darwinism – but she does so in a less sensationalistic way than many.

There are also a lot of resources from the dog world, in part because rigidly closed registries have long been the norm within that community. One of the best sites for articles was the (now-defunct) Canine Diversity Project.  Among the particularly good ones are:

The Poodle and the Chocolate Cake by Dr. John Armstrong  (a really good overview of the problem)
The Price of Popularity: Popular Sires and Population Genetics by C. A. Sharp

The dog world has also had some interesting experiments with out-crossing. Closed registries are the norm for dogs, so these have all been very controversial. Among horses relatively few breeds maintain completely closed stud books, and fewer still are willing to pay for that choice in the way that dog breeders are.

The Backcross Project  (restoring proper uric acid levels to Dalmations)
Bobtailed Boxers
(This series is worth reading just to see how quickly a breed reverts back to type when crossed on something really different, all extensively documented in pictures.)

There was also a great post on the Terrierman blog about the importance of provenance in selling breeds.
You Can Blame Garrison Keillor’s Grandfather
The Terrierman blog has a lot of great posts about genetic diversity, though that recommendation comes with two caveats: 1) the blog is routinely sprinkled with unrelated politics that readers might or might not appreciate and 2) temperance and diplomacy are not really the style there. (He also takes exception to the color merle, which of course is not going to fly around here at the House of Blue Dogs!) Still it is consistently an interesting read, and it is worth exploring the (vast) archives there.

There is also the BBC program “Pedigree Dogs Exposed” which one of the comments referenced. To say that the program ignited a firestorm would be an understatement, and in parts it is certainly sensationalized. Still, what it portrays is happening, and perhaps something like this was the only thing that would push people to look at the issues involved. Since it aired, studies have been conducted and some preliminary actions taken by the British Kennel Club.

So what does that have to do with horses? To some extent horses and horse breeds are in better shape because they have not had a uniform culture of closed registries. Still where there are small populations and closed breeding programs, the same kinds of issues arise. Here is a discussion of the Friesian stud book policy on genetic disorders. This statement shows the very real parallel with the problems facing the dog world:

For this reason, the KFPS believes that carrier stallions should remain in the breeding pool. In addition, it should also be possible to approve young carrier stallions on the condition that they possess extra qualities. If we do not implement this policy, 1 in 3 young stallions will automatically be rejected on the basis of DNA testing.

One in three. And what are they carrying? Dwarfism. Twelve of the current stud book stallions are carriers of dwarfism. Hydrocephalic Foals. Sixteen of the current stud book stallions are carriers of hydrocephalism. The effective breeding population is too small, and the defective genes so widespread that culling the carriers would probably narrow the gene pool enough that new defects would appear. That is what has happened in many dog breeds. It is exactly what should concern horse breeders, particularly those working with rare breeds with limited populations.

That is why many rare horse breeds have actually relaxed their color restrictions. They may still have strongly worded preferences for colors or markings, but off-colored or mismarked horses are not automatically removed in many breeds. Ironically, one of the breeds that does do this is the Friesian, which does not allow chestnut carriers as breeding stallions. This puts the registry in the awful position of permitting damaging defects if the horse is otherwise “of good quality”, but banning something as inconsequential as color no matter how nice the horse. As with dog breeders, this kind of disconnect with simple animal welfare undermines the assertion that purebred breeders are guided by a higher standard of ethics than “backyard” breeders.

Were it possible to expand the gene pool, culling could be accomplished without raising the inbreeding level to still more dangerous levels. Even without outright culling of carriers, introducing an outcross line can dilute the overall incidence of the defective gene. The fact that there are animals breeders out there who will choose “purity of blood” over solving serious health issues is something that deserves more attention. It isn’t a particularly comfortable discussion for a lot of breeders, and it points to the need for a very different mindset when it comes to breed stewardship, but it is one I personally feel must happen.