Breeding protocolsgreenspun.com : LUSENET : ASD : One Thread
I apologize if I misinterpreted the goal of the Genetics Committee recommendations. It appeared to me to be that the goal was to eliminate the ASD gene, and along with it the silver dapple gene, not just reduce its incidence. Since the idea was to increase aa horses, I understood that to be the case. I have not actually seen a copy of the final draft. It would be nice if it could be posted on the site for review and comments. It would be much better to have the most recent information available rather than the draft that is the last information available to us to post.
If AA to aa is going to be allowed for mares, it should also be allowed for stallions, for the same reasons, if they are horses that should otherwise be permitted to contribute offspring to the gene pool because they have desireable characteristics of gait, temperament and/or conformation. (Not necessarily in that order.) The problem of having enough normal horses to breed to is a self limiting problem, the aa's will get bred, and that will be it. Moreover, there are far more mares than stallions, and the mares are much more likely to be non-silver dapple than stallions. I am concerned about deleting from an already small gene pool good stallions, with only a one year transition period to try to breed for Aa replacements of those horses.
I agree with Paula that all the Aa offspring of AA to aa will need to be bred to normal horses, but half will be colts, most of which will be gelded, and only a few will be used to replace the AA stallions they were sired by. We should not dump out otherwise good horses from an already too small gene pool. My position is that we need to allow the genetics of the AA stallions to be continued in the gene pool for longer than only one year, perhaps not indefinately but for five, or even three years, to allow the breeding of their replacements, by Aa sons. Maybe the breeding of AA stallions should be allowed only for those that do not yet have an Aa son that is a stallion. As Paula herself notes there is nothing wrong with producing an Aa horse from the point of view of the horse's health, but I also do agree with her that we do need to be concerned from the point of view of the proportion of AA, Aa and aa horses in the population. Again, perhaps it should only be allowed for a longer but still limited time, and/or restricted to those that have not produced an Aa stallion quality "replacement" son.
Paula is correct to point out that we can not analogize too closely to the canine model and in her reasons for saying that. I support the overall goal of reducing the incidence of the ASD gene in the gene pool. I further agree with her that the The problem with breeding AA to aa is not what it does produce, it is what it dosen't produce, ie, aa. That is indeed a definate drawback. But the Aa to Aa breeding that is part of the Genetics Committee Recommendations has the problem of what it DOES produce. Does the evil of inflicting 25% of the offspring to the known effects of ASD justify the production of 25% aa? Not to me. I would far rather breed for Aa's, where I know that neither the horse nor the owner will be harmed by that state. I think any proposal, whether mine or that of the Genetics Committee, will require policing, by requiring eye exams, requiring that the offspring of forbidden breedings will not be certified to breed, and backed up by parentage verification at or even before certification to be sure all are abiding by the rules.
Paula expresses the opinion that there are enough Aa horses and AA mares to guarentee the availability of chocolate. It is important to understand that I am not all that interested in chocolate. I just see no reason to breed it out when so many others do like the color, and when Aa horses are not adversely affected by carrying one copy of the A gene, even now that I know that it is not the objective, I remain concerned about abruptly deleting from an otherwise already small gene pool horses that have otherwise been bred for other desireable characteristics, of gait and temperament. I do not mean this in any way to be offensive, but if the only place you have seen these horses is in Kentucky, you may well get the impression that there is about nothing else out there but chocolate. I could be wrong, but I think that there are a lot of non silver dapple horses, mares in particular, that are outside of Kentucky. Even in Kentucky, the big farms tended to put their chocolates out front, and their other colors in the back. I have a feeling those other colored horses are suddenly going to find themselves out front, and instead of bragging about how many chocolates they have we are going to see bragging about how many non silver dapples they have! In Wisconsin there was for several years a concerted effort to bring in mares on the basis of gait and temperament, and very few were silver dapple. Trouble is, the few stallions that are there are mostly silver dapple, so far as I am aware, and if the AA stallions are eliminated from breeding, then the percentage of the stallions eliminated for breeding could have a signficant impact. That impact is true elsewhere as it is in Wisconsin. I do not disagree with a goal of decertfying AA stallions and I certainly support restricting their breeding to aa horses only. I do not take the position as a breeder that this is someone else's problem while I produce mostly Aa horses. I too agree that the goal of reducing the ASD gene is one that all breeders must work for. That is part of the reason I would agree to a time limit on the use of AA stallions, for a phase out period, but I feel very strongly that one year is not enough time. Paula expresses concern that we can not pretend to be serious about this problem and impart this seriousness to members and buyers if we continue to allow AA stallions to be bred. I have three responses to that. First, I now see that the breeding of AA stallions to aa mares can not be continued indefinately. I have modified my position to ask for a phase out period,something longer than the one year proposed, but no more than 5 years. I have heard some support for the three years that I suggested. Second, the use of the AA stallions is self limiting, in that they could only be bred to aa mares under my proposal. Third, we are going to have a problem justifying to the public allowing AA mares to be bred indefinately. Perhaps it is enough to answer that mares produce fewer foals in their lifetimes, but perhaps we should be considering a time limit on those breedings, too. The biggest problem we are going to have is that we are going to have a very hard time pretending to be serious about the ASD problem and imparting that seriousness to buyers if we allow Aa to Aa breedings, where a concious decision is being made to subject 25% of the offspring of those breedings to ASD, more when the accidents that will happen due to 20% of the breeding pairs being AA rather than Aa. There has been almost universal revulsion in this group to that idea. My proposal at least has the advantage of only producing Aa foals.
-- Annette L. Gerhardt (firstname.lastname@example.org), January 03, 1998