Hi all, I recently read an article in the Paint Horse Journal , July 2007 issue, about the HERDA gene. Naturally this was after I bred my mare, who may be a carrier. After reading this article, I did a search on this website about the same topic, and I still am somewhat confused. Both articles say the the gene is 95% directly linked to Poco Bueno through (both their sires and dams) My mare has Poco Bueno only on her mom's side (5 generations back) her dad doesn't have Poco Bueno on his side at all. I do plan on getting her tested for future breedings, but what are her chances for being a carrier and thus her foal being a carrier? There are parts of these articles I don't understand. Like when they say, " When an afflicted horse is crossed with a normal horse, 100% of the offspring will be carriers. That doesn't make sense that a carrier to a non carrier would produce 100% carriers. It this helps this is her pedigree http://www.allbreedpedigree.com/tulips+ta+kiss+ya Help me to understand please! Also her sire is an overo. I can't find any information on whether or not he was tested for the OWLS gene. I haven't been able to contact the owners. Do the same statistics apply for this gene? As in both parents must be carriers for the foal to be born a lethal white, etc.? Does anyone know how I can find out if her sire was tested for the OWLS gene?
I think that 100% of the horses will be carriers because HERDA is a homozygous gene and therefore all horses who carry it, will give it to the next generation.
Im not sure whether the APHA can help with the DNA testing situation on the stallion. All stallions registered with the APHA have to have DNA testing done to be approved stallions, and all have to be tested at APHA approved laboratories, however, I do not know whether OWLS is done or not. You can always contact the APHA to find out.
There are good articles about HERDA to be found on line at UC Davis and on another site that is actually dedicated to providing information about HYPP. For images of HERDA, visit "The Horse". (Follow those links).
Thanks Jos and Debbie, after reading the articles again I think I understand better now. If an afflicted horse (one that has the disease), is bred to a normal horse (one that is negative for the gene) then 100% of the offspring will be carriers. So in my mares case, if she does carry the gene, and the stallion doesn't, then the baby will have a 50% chance of carring it without clinical signs, but will not express the disease. Does this sound right Jos? Would the same thing apply for the OWLS gene?
Charlene: I think if I understand it correctly, if your mare is a carrier, your foal will also be a carrier. I think Herda is a recessive gene, so it may take another carrier for it to show, but your foal will carry the gene 100% if the mare has it.
Jos, correct me if I have that wrong. I have always stayed away from that particular line of performance horses. I heard about it years ago from a breeder down in the states that had been breeding performers for 25 years. He mentioned the bloodline and I have steered away from it ever since.
If one of the parents has the disorder (is afflicted), and the other parent is not affected in any way (neither afflicted nor carrier) then 100% of offspring will be carriers;
If one of the parents has the disorder (is afflicted), and the other parent is a carrier, then 50% of the offspring will be afflicted and 50% of offspring will be carriers;
If both parents are carriers (but do not have the disorder - i.e. not afflicted), then 25% of the offspring will be afflicted; 50% will be carriers; and only 25% not affected in any way;
If one of the parents is a carrier (but not afflicted) and the other parent is neither afflicted nor carrier, 50% of the offspring will be carriers (but not afflicted).
This can be worked out using a "Punnett Square", where: HH = Afflicted HN = Carrier NN = Normal (not afflicted or carrier)
It would look like this:
The left and top "H" and/or "N" reflect the parental status (doesn't matter which goes where) and the rest reflect the offspring possibilities. You can play around with other variations if you like, by placing the applicable H or N combination in the positions to the left.
Debbie, I think your right. I haven't had her tested yet, but I hope she is negative. I just recently heard about it in an article in my Paint Horse Journal. I will be testing her shortly, and will let you know. If she is a carrier, and her baby is a carrier, then I will just have to not breed her to those lines. Even if she is negative, I probally still wouldn't breed to those lines.
Posted on Wednesday, December 05, 2007 - 12:04 am:
Thanks Jos, that is what I thought. So if my mare is a carrier and the stallion is definately not, then there is a 50% chance the baby will be a carrier but not afflicted, right? Does it work the same for the OWLS gene?
Posted on Wednesday, December 05, 2007 - 11:52 am:
As noted, you can create other possible results in the Punnett square yourself...
I think the same will apply for LWS, but I am neither a geneticist nor a Paint breeder, so my knowledge of that particular genetic issue is a little cloudy, and a quick search to determine the actual status of the deficient gene shows that others are too...! I therefore stand to be corrected on the LWS issue - there are others on this board who will be able to give you a definitive answer, I'm sure.
The difference with OLWS is that an affected horse dies within the first few dies of it's life if not put down. You then don't have the problem of breeding affected horses. So the chances for the gene being passed on or affecting the foal are as follows The resulting foal from two carriers of OLWS would have a 25% chance of having OLWS and therefore dieing, 50% chance of being a carrier and 25% chance of being clear or negative. One carrier and one non carrier would produce 50% carriers and 50% non carriers. Hope that helped.
Thanks Emily, When I said, "does it work the same for the OWLS gene?" What I meant was, what you were talking about in your second paragraph. You just confirmed what I thought that if a carrier is bred to a non carrier then there is a 50% chance of being a carrier and a 50% chance of being a non carrier. From what I been reading an horse born with OWLS dies within the first few hours because, it can't poop. With the HERDA, they die eventually, usually by the age of two they have to be put down.
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