Thursday, February 2, 2012

Shopping For Nice Genes

Equine genetic disorders. Nothing gets horse people fired up quicker than a debate on genetic testing, and in recent public social media forums, the topic has been a hot one lately. We have been there before; we've seen HERDA in the Poco Bueno's, SCID in Arabians, HYPP in the Impressive's, JEB in draft horses, and others, so we shouldn't be surprised that this topic has come up yet again, with the call going out demanding mandatory testing of all breeding stock. The nasty culprit this time is GBED, as well OLWS, both of which have become more prevalent in recent years.

Genetic mutations that cause disease and/or birth defects have always been around; DNA is no more a perfect system than any other within a living being. What has changed in modern times is the speed at which these flawed mutations can spread. Prior to the development of artificial insemination and embryo transfer, stallions could only breed so many mares, and mares could only produce so many babies. The odds were much lower that a stallion who was a carrier of a disease gene would meet a mare who happened to be a carrier of the same recessive disease gene and produce an affected foal. Of course, veterinary medicine evolved along with these diseases, so that many years ago, vets might not be able to connect all the dots in tracing a genetic defect, but now they have the capability to know without a doubt what is wrong with an affected foal, and trace the origin of the gene. Another factor that has increased our exposure to genetic diseases is that many modern breeders follow trends in which stallions they choose for their mares. If Stallion X has made a ton of money in the show pen, or has sired horses that have, everyone has to breed their mares to him. This dramatically reduces the number of animals in the gene pool, and accelerates the distribution of diseased genes.

These disorders are pretty horrible. If you have ever seen a horse suffering an HYPP seizure, you know what I mean. When a horse has HERDA, their skin and underlying tissues fall off and cause terrible scars. PSSM sentences the horse to a life of chronic pain and the owner to providing the horse with a special diet to control symptoms. Foals with OLWS, GBED and SCID are doomed from birth, and they have no hope for survival or any quality of life. It would seem a foregone conclusion that we want to avoid these scenarios at all costs. Yet they persist. Why?

To find the answer, you have to look at the problem from both the mare owner's side, and the stallion owner's side.

Stallions can produce many more babies than an individual mare can, so a genetic disease is often statistically found faster in a stallion's breeding career than through a mare's, since mares only average a few foals in a lifetime. I think this gives some mare owners a false sense of security. They (wrongly) assume that a stallion owner would know if their stud is a carrier, and they (wrongly) expect that this information would be made public.

I have also heard mare owners state that since she has not produced an affected foal yet, that chances are she won't produce an affected foal next time. This is a fallacy based in ignorance. If you put any two sets of recessive genes into a Punnett square, you will come out with the same odds for every breeding; 25% of the foals will be unaffected, 50% will be carriers, and 25% will be affected foals. Each breeding is statistically independent – each roll of the dice carries the same odds. You could breed two carrier horses to each other twelve times, and you might see 12 unaffected foals, 12 affected foals, or distributions from all three possibilities. If you firmly believe that you will get lucky every time because you got lucky before, I bet the dealers at the craps tables in Vegas love you!

I think many people don't know what resources are available to them for genetic testing, or understand how easy it is to have done. This is fairly new, and since registries and horse associations haven't pushed it – after all, who wants bad publicity – many don't test because it is just too much of a bother to figure out this new-fangled technology and seek out help. However, both the American Quarter Horse Assn.* and the American Paint Horse Assn. have begun to provide kits for people to use, and there are also several private labs that can do the tests quickly. The tests aren't exactly cheap, but certainly compared to the cost of having a dead foal, testing looks pretty inexpensive.

Now, the tricky part....getting stallion owners on the genetic testing bandwagon. I have heard many times that this is a taboo subject, that demanding industry-wide testing will never go over with the heavyweights in the business, and that bringing it up will get you blacklisted from the industry. The source of this resistance is fear. People are naturally afraid of change. Individuals who have reason to believe their stallion is at risk of being a carrier resist that knowledge, fearing the stigma that will be placed on their horse, the loss of income and the smearing of their horses', and their own, reputation. When this fear is put under the hot lights of debate, the result is often a vicious lashing out against the knowledge, and the people responsible to bringing the knowledge to light. Some stallion owners have more to lose than others, and as they say, the bigger they come, the harder they fall.

My response is that the truth always comes out. Stallion owners – wouldn't you rather disclose something like that yourself, where you have control of it and can even spin it in a positive way, since you will look more responsible to the public? Or would it be better to wait, constantly worrying about it, risking the loss, whether it is your foal that dies or a valued customer's, and having the truth get out? What if it is found out that you knew your horse had a problem but you chose not to disclose it, and then are hit with a lawsuit? Won't that have a worse effect on your reputation and your horse's legacy? Willful ignorance makes not only the individual stallion owner look bad, it damages the entire industry. People don't want to be associated with a group that clings so tightly to the all-mighty dollar that they are unable to be ethical.

I do have a couple of caveats to my arguments for genetic testing. I have heard people say “There oughta be a law...” I do not think this is something that should be legislated by the government. The government has no business in horse genetics, and even a registry doesn't have much legal authority over how people breed their horses. Can they strongly encourage it, and make it easier for people to do? Sure, but I doubt they could require it. Since there are only a small percentage of horses out there that are carriers, and only a percentage of them will mate, and then there is only a 25% chance that the pairing will result in an affected foal, it doesn't make financial sense to require it of everyone. And if registries require one disease to be tested for, shouldn't they require all those diseases that can be tested for to also be included? Where would that end? I have to wonder if required testing by a registry would open them up to some type of lawsuit; after all, simply putting a sticker on a horse's papers does not imply that the registry is then responsible for people's breeding decisions. I am sure that there are people out there who will breed to Stallion X anyway because they believe it won't happen to them. It might better serve the public if more effort was put in to education versus legislation and more rules.

I also do not feel comfortable 'outing' any horses out there. It is completely up to the owner to seek out that information and disclose it. Unless I personally pull hairs out of a horse's tail, send it in and see the results, I do not really know what that horse's genetic make-up is and if I make a supposition without knowing for sure, I am committing slander against that horse and owner. We have to understand that in this business, it pays to spread rumors about your competition, and people who point fingers at others often have their own agenda. I don't want to be part of a witch hunt, I am just advocating for better business ethics that lift up our industry, rather than diminish it. If we have widespread, mandatory testing, it may then become a possibility that there would be pressure to ban those animals that test positive as carriers, and I am not sure that is right. First, it would further shrink the size of the gene pool, perhaps making other disorders more prevalent, and second, it would remove some very successful and popular bloodlines from public use, which does not necessarily push our efforts forward. The object is to control the spread and try to prevent affected foals from being born.

The only way things will change with the current attitude toward genetic testing is if it makes more financial sense to test than to not test. If mare owners feel strongly about this subject, then they should test their mares, and they should breed to stallions that test and disclose. And many will do this! If there is an added benefit to all the fighting going on over this subject, it is that more people will find out the facts about genetic disease. It is my hope that mare owners will educate themselves and that stallion owners will see the changes on the horizon, and become more proactive in their planning. Perhaps if we all did this, we could avoid yet another scandal.....

*I have been told that AQHA has started making genetic tests for all possible diseases available, but I could not find anything on their website referring to an expanded test.  Currently, all Quarter Horses seeking registration must be parentage verified through a DNA test, and if the horse is a descendant of the stallion Impressive, the horse must also be tested to establish its HYPP status.