Friday, February 6, 2009

Killer Genetics

Since I am on a roll with the genetics thing, there is a list of the 6 genetically linked...and lethal conditions that are prevalent today. If anyone knows of any others, please list them in the comments!! I'm not going to get too descriptive about them...cause there is info all over the net to read and digest.



HYPP-Hyperkalemic Periodic Paralysis...aka "The Impressive Gene". This disease orginated with one stallion-Impressive. This is the only genetic condition of the 6 that is not 100% lethal. There is a test. Horses that are N/N CANNOT pass the gene or the resulting condition down. N/H horses can pass the condition down and may or may not have symptoms. H/H horses are dominant for the gene and every single one of their foals will be N/H or H/H(I think that is right?). These horses are symptomatic and can die or will eventually die because of it. There is a test.



SCID-Severe Combined Immuno Deficiency. To date this condition only affects purebred Arabians, but there are studies that indicate that other breeds may also carry the SCID's gene. There is a test.



OLW-Overo Lethal White...aka "Lethal White Syndrome". Primarily this has been an affliction for the Paint Horse Association, but now that the AQHA has lifted it's maximum white rule, we are going to see problems with it in QH's now too. This is a recessive gene, so can only cause problems when 2 recessives are mated together. There is a test.



HERDA (or HC)-Hereditary Equine Regional Dermal Asthenia. This is linked to QH's that descend from Poco Bueno and I saw on one article...Doc O' Lena? This is a recessive gene. There is a test.



GBED-Glycogen-Branching Enzyme Disorder. This condition has been traced to Zantanon, through his son, King-P234. Only about 8% of the decendents of King carry the gene. I don't know how they can say that, because I suspect very few of the total number of descendants have been tested. This is a recessive gene. There is a test.



JEB-Junctional Epidermolysis Bullosa. This condition affects the foals of Belgins and American Cream Drafts. It's possible that it has been found in some saddlebreds as well. But it actually affects 25-30% of the population of these two breeds. I don't now if there is a test, but I presume there is.



Again, all of these diseases are 100% lethal, with the exception of HYPP.



JEB, GBED, SCID and OLW exclusively affect foals. All result in the eventual death of the foal.



HERDA may not be noticeable in all foals, but becomes apparent as the horse matures. I suspect that there are some horses who live longer than others, but inevitably they all eventually have to be euthanized, or should be(who wants to look at your horse with it's skin peeling off-gross!!).

The perpetuation of these known killer genetics ultimately comes down on the breeders. But I also feel that once a breed organization knows about them, registration of afflicted bloodlines(or color patterns) should be contingent upon the proper testing and all testing be stamped right on the papers. The breed organizations are afraid to force the issue for fear of driving members away. But if the AQHA, and every breed organization that recognizes the use of QH's for breeding purposes takes the same stance at the same time, people will either be forced to acknowledge their crappy breeding practices and stop or they will get out of the horse breeding business...a win, win in my book.

The one question that people may ask is why now? Why are all of these genetic disorders becoming so prevelant now? In my opinion, they have always been there. Almost all domestic animals carry recessive genes for some sort of genetic disorder. In cattle, they test for recessive genes by breeding bulls back on their own daughters. This normally brings any recessive genetic disorders to the surface and can determine whether a bull is kept or not. So right off the bat, they inbreed to check for genetic purity and then proceed forward. Linebreeding can hide the genetic disorder for generations. But eventually it will come out. Since the equine breeding programs have moved away from inbreeding...where recessive genetic disorders become immediately apparent to linebreeding, those recessive traits are only now becoming a problem. Another major problem, as I see it, it that there are a lot of breeders out there these days that just don't cull aggressively enough. Since the incorporation of the Foundation Quarter Horse associations...people have become more concerned with percentages than the actual physical attributes of the horses that they are putting into production. Mares that normally never would have been bred are popping out baby after baby and stallions that obviously should be gelded are siring tons of mediocre foals.

If you look at what the "foundation" breeders did in terms of inbreeding and linebreeding, it is pretty obvious that their intention was always to create a better horse than either the sire or dam. They were actively trying to perpetuate greatness. I have no doubt that they faced a lot of the same problems as breeders today, the difference is they were okay with sub-par individuals disappearing from the history books. Another interesting fact to note is that breeders used to recognize the importance of "the outcross". Inbreeding and linebreeding were okay, but when they got what they wanted, they sought out a complimentary outcross to create hybrid vigor. The resultant product often exceeded both the inbred parent and the outcross parent. That was the whole purpose.

19 comments:

ezra_pandora said...

Wow. Thank you for listing all of those. I had only heard of the HERDA and HYPP. had no clue of the other ones, but I will be looking them all up. Very interesting.

Leah Fry said...

I always say I learn something new every darn day. Thanks for my new thing(s) today. I googled the ones I didn't know about.

Mrs Mom said...

Awesome info once again BECG! Thank you!

Wasn't there a question raised on one of the other blogs a bit ago now, about a heart condition found here and there in N/N horses? Linked to HYPP? Or is my brain just not working right there? I was unable to follow the entire conversation that generated, and am hoping that you or someone here knows the facts on that. Having a horse who is N/N BUT fairly heavy in Impressive genes, it seems like a smart thing to know! ;)

Adventures Of A Horse Crazed Mind said...

Another great post. I agree with you 100% about the registration thing... AQHA is insane not to enforce it! So much for doing what is best for the breed!

BrownEyed Cowgirls said...

Ezra-I've been around King and Poco Bueno bred horses all my life and I have never seen a HERDA horse. It's hard to tell about the GBED thing though??

Leah-Hey...glad to be of service.:)I had to google the Draft horse one. I had never heard of it before.

MM-We did hear some scuttle-butt about N/N horses having "other" issues. Personally, I think there is a lot more to HYPP than just the obvious and if these people are going to continue to linebreed horses with an obvious genetic defect, it will continue to manifest itself.

Horse Crazed-I get so disgusted with the associations. Their JOB is to protect the integrity of the breed. Why spend millions figuring out what these defects are and how to stop them from happening if you are not going to actively recognize the problems they cause and take steps to eliminate undesireable carriers from the gene pool?? People have a very misguided sense that just because their horse is registered, they don't actually have to put any more thought into breeding than what color the baby is going to turn out to be. I know there are alot of good breeders out there. But even they are contributing to the problem because of the sheer volume they are producing.

We figure it is better to produce a few really good ones rather than produce a whole bunch of average. And we also know that the horses we produce are not everyone's cup of tea, but they work for us and since we are the ones that use them...that is all that matters. If there are other people out there who get along and appreciate what we raise-great. If not, at least I will never have to go buy a horse and wonder what it will turn into. I know it sounds rather arrogent, but you won't ever find us having to dump a horse at a sale either.

cdncowgirl said...

I agree with you on the point that the breed associations need to step up and take preventative measures.

Melanie said...

Brava!!!
I just read your last post along with this one, and you did an excellent job of explaining all of the various genetic anomolies/abnormalities that can occur among the various breeds of horses that are out there!!!! (sheesh that was a mouthful...lol!!!)

Like everyone else, I agree that breed associations need to step it up a bit. And goo dfor you for being a responsible breeder!!

Now...if I could just figure out a way to get one of your horses to WA...lol!!!!

Keep up the great posting girl!!!

Natarojo said...

Your posts are always so informative. I don't often have the time to read up on certain things that I'd like to learn more about. I have a really hard time with the AQHA not taking the initiative to take action and enforce these things!

manker said...

wow great info ... agree with breed associations being more proactive on this...

thanx for news we can all use
gp in montana

Train Wreck said...

One of Cowboys cousins bought a beautiful, gelding one year. The guy wasn't sure how he was bred? Not sure how that all happened? But this horse was gorgeous, perfect quarter build and flashy. Gentle trained well easy rider, No faults. Till the papers. Impressive, I knew nothing about this linage until then. He ended up selling him because he didn't want to have any problems. It was really a sad thing. such a shame. Enjoyed reading up on these disorders and such, So when is your clinic??

Saddle Mountain Rider said...

Again, an interesting blog to read. For those of us who love quarterhorses, your blog raises some interesting points. That's one of the reasons that i nominated you for the lemonade award that you can pick up at my blog.

kdwhorses said...

Very interesting posts and educationl as always! I'm going to have to go back and reread your last couple of posts when I can sit and absorb them!

Andrea said...

Our Stallion is OLW carrier. My husband has had the stallion since he was two years old. And my husband never ever had a LW baby. Until three years ago. We bred him to a white unregistered mare. We all thought the mare was an appy mix of some kind. When she had her foal it was solid white and very sick. We went with her to the vet and the foal had to be put down. The owners didn't want to rebreed to our paint so we offered them out QH stallion instead. She agreed to that.

But my husband had never encounted a LW before, so I had to educate him on it. We now let people know that our stallion is a OLW carrier and that they should have their mare tested. If you do breed your mare that is a carrier to a stallion that is a carrier, there is a low percentage rate that the baby will be a leathal white. But, it's a risk. So, we loose a lot of breeds that way. But there are sooooo many overos that are LW!! It's amazing.

The stallion I breed my TB mare to was a LW carrier. And he is Impressive breed. I was just batting 1000, wasn't I? LOL!!

I always swore I would never own an Impressive horse, and I am about to have a foal on the ground in a few months. I have my fingers and toes crossed for sane babies. I have always found Impressive foals to be a bit more edgey with their temperments.

I love your breeding posts. They are fun to read.

ezra_pandora said...

Ok, so now we know about the desireable and undesireable sires. Do you have any well known dams that were top notch or really bad? You never hear anything about them, just the boys.

(I'm going to post a questions that somewhat has to do with this on my blog later today)

Callie said...

Wow! Great post! I've heard of all of them. There is that one also that I recall Mikael posting about. Lavender something in Arab foals? I think. I came real close to and now regret.I found a double Impressive bred mare(top and bottem) at auction, not in the best of shape, but I know in my heart of hearts I could have gotten her healthy, but my friend restrained me. I would have payed $200 for her and certainly not bred. Her papers said N/N, I just liked her. She was pretty and needed me and I regret not forcing my hand and just taking her home.

BrownEyed Cowgirls said...

Ezra-Ohhhh-the "blue hens". I love those girls. There are quite a few and I will certainly post about them.

Andrea-I think they still have a LOT to figure out about the LW gene. I trained for a Paint horse breeder(before they had a test for OLW)and he had two stallions-1/2 brothers(same sire). Their mothers were bred differently from each other. So he switched and bred the mother of one stud to the stud no related to her. No inbreeding-as the mares were not related in any way. One mare produced a solid and a loud overo. The other mare produced LW foals both times.
The thing I found interesting was that the sire of the two stallions had produced LW foals in his lifetime. Each of these mares had produced LW foals previously. It's pretty obvious that they were all carriers. So why did one nick not produce LW foals and one nick produce homozygous for LW foals? There has to be more to it than just being a carrier.

Callie-you are right-I do remember MiKael talking about the Lavender foals.

Paige said...

The reason AQHA wont deal with HERDA so far is that they put so much money into UCDavis doing the testing, and then UCLAs test is flawed, and that is because they got beat to the punch in developing it and hurried along. What they have is not a reliable test, and I can back that up with several false results.

Patents are pending on the Cornell test right now- and it is a lengthy process. Wait until those things are done, and perhaps AQHA will do something--but I bet you it will be notation of test results and not exclusion from the registry

This is one area I know inside and out, and if you had any idea the things going on behind the scenes, you would be sickened.

I have seen a lot of affected horses, and there is a huge range of how damaged they are by the disease--it is really fascinating

There are some experimental things happening this season related to early detection that will change the way HERDA is dealt with if it works as well as it is hoped to. Stay tuned!

BrownEyed Cowgirls said...

Paige-Thank you for the input. It helps a lot to have someone who has actual knowledge talk about these things.
I don't wanna know...I have seen enough sickening things in the horse biz to last me a lifetime!!

Rising Rainbow said...

Great post! And timely too, with breeding season coming on we all need to be thinking about genetic faults.

Lavendar Foal Syndrome is the name of the disorder that Callie remembers from my blog. It is found in straight Egyptian horses and crosses from straight Egyptian horses. It is an extreme neurological disorder and the foal must be euthanized at birth.

You are right about SCID in horses other than Arabians. However, all of those horses will trace back to an Arabian that carried the recessive gene in the first place.

Some people breeding half-Arabians for the show ring don't think they need to test their breeding stock for this gene but that is a fallacy. If crossing two horses with Arabian blodd anywhere in each horse's pedigree, you need to know the status for SCID.