Monday, June 18, 2007

What to Do with Carriers of Lavender Foal Syndrome in Arabian Horses

The series on LFS began with the post Lavender Foal Syndrome - An Arabian Horse Breeders Nightmare followed by Breeding Carriers of Lavender Foal Syndrome in Arabian Horses

Once an Arabian horse has been identified as a carrier of Lavender Foal Syndrome, the next question is what do you do with that horse.Some people think that all known carriers should never be bred again to eliminate the gene.

There are huge problems to that line of thinking. While a defective gene may be eliminated a bit sooner than if carriers are bred, many useful genes are being removed from the gene pool as well. And it must be remembered, that by never breeding a known carrier to a known carrier, it still is possible to eliminate the problematic gene.

How long it would take to eliminate the problematic gene either way would be an impossible guess without knowing the actual number of carriers. But I was very surprised to learn at a conference on SCIDS how short the time to eliminate that gene would be with responsible breeding. Because LFS is far more rare than SCIDS, I would expect in even shorter time frame would be likely.

To understand the problems with eliminating all carriers from breeding, you must understand some of the facts about the Arabian horse and it's genetics. The Arabian horse has the most limited gene pool of any breed of horse. Other breeds have been contrived from crossing one type of horse (one gene pool) with another (second gene pool) to produce a specific model (more diverse gene pool). Incidentally, most light breeds will trace back to an Arabian horse in their blood. The Arabian horse, however, is as Mother Nature created it.

We humans over the centuries have selectively bred the Arabian horse for specific traits to refine the horse to our needs or desires but we have never gone outside the gene pool that Mother Nature created.

The integrity of that gene pool has been protected over the centuries and continues to be protected by the Arabian Horse Association. Preservation of the Arabian horse is that organization's utmost goal.

Arabians are the earliest known breed of horse and its blood is pure. That is pretty much the mantra of AHA and other Arabian breed organizations around the world. There are no, nor can there be, any provisions for out cross to correct issues with in gene pool of the Arabian horse. To do so would eliminate the Arabian horse. It is what it is.

Keeping this in mind to no longer breed carriers at all is to eliminate all their genes from the gene pool. This would make this already limited gene pool even more limited. That would open the door for other recessive, non-desirable traits to be strengthened.

Think of it as concentrating the blood. Once you remove the carriers, you are left with an even more closely related group of horses than you had before. You have removed some of the diversity from the gene pool making the doubling of recessives more likely.

Some breeding programs practice inbreeding. The purpose of inbreeding is to strengthen suitable desirable traits that are recessive in nature. But inbreeding also strengthens recessive genes that are undesirable. The breeder who knowingly practices inbreeding doesn't get to pick and choose. There is always an unknown risk. That inbreed offspring can turn out really fantastic or really, really awful. Seeking that outstanding individual, those breeders are willing to take that risk.

With the concentration of the gene pool caused by removing carriers, it's like forced inbreeding only it's forced on the entire breed instead of selective inbreeding by some individuals. The effect will be upon the entire gene pool of the Arabian horse instead of just one herd.
The mathematics involved tell us that effect would be dramatic This close breeding makes it easier to match up recessive genes because concentration makes them more dense in the sample. Somewhere down the road could be a disease or diseases or other genetic flaw even more devastating than LFS just waiting for the right combinations of recessives to be paired for the problem to emerge.

Removing carrier horses from the gene pool could be devastating to the breed.The health of the gene pool of the Arabian horse is dependent on keeping as many viable breeding horses active and participating as possible.

Knowing that it's important to keep breeding carrier horses to maintain the diversity of the gene pool, breeding decisions regarding these horses need to be made in an informed manner. Far more accurate and healthy breeding decisions can be made with knowledge than with guesses.

Once a test is found, those horses will be able to breed to clear horses knowing the variety of our gene pool is being protected without it being at the expense of people's hearts and the proliferation of this toxic gene. In the meantime, the health of the gene pool will be dependent on breeders being open and honest about LFS so that others can make as informed decisions as possible until a test is available and still use known carriers as breeding stock.

Because it is so rare, there are few cases to study to garner data needed to establish reliable information. Anyone having or who knows someone who has had a lavender foal is requested to contact researchers to help find and isolate this killer of Arabian Foals.
For more information on Lavender Foal Syndrome

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  1. Thank you for the in-depth dicussion on LFS and all of the information available. I had not heard of it before Shina had her foal, but then, the world of breeding horses is not something I was involved with before finding marestare. And Arabians are a horse that I am now just learning a lot about. Thanks so much, will be checking back here again!
    PS. Love your twins, too. Glad they are doing so well :)

  2. Lavender foal syndrome isn't that rare, it's just been covered up for DECADES! It goes back to Nazeer. The big breeders have been covering it up for years, threatening to sue anyone who mentioned it. The only people who were honest about it were Bentwood Farms, they publicly admitted when it showed up in their herd. It's a recessive, so 3% of the straight egyptian and egyptian-related population will have it. The only hope is for a DNA test like they have for SCID.