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WFFS positive stallions

How are breeders handling positive stallions as far as using in their breeding program? Assuming a mare is tested negative, do you go ahead and use or decide not to introduce into your program? Is it relevant if you are breeding for possibilily keeping the next generation in your program vs breeding to sell as a performance horse prospect. Thoughts appreciated.

There are no WFFS positive horses. There is no documented case of a WFFS positive surviving to adulthood.

As far as carrier stallions, we have no issue using them. We test our mares and would never breed carrier to carrier, so there is zero chance of getting a positive foal even with a carrier stallion. And since 50% of foals will test clear, you may be good. Either way doesn’t bother me as long as I’m informed and can make an informed decision. If a stallion owner doesn’t want to list their status, I just move on.


I’m seeing most breeders are testing their mares and making decisions based on the results; there’s some movement on FB (especially in Dressage Breeder’s Group) for more transparency from SOs about a stallion’s WFFS status.

I’ve wondered before about what carrier status does to a horse; we really don’t know. It would be my preference not to breed a carrier at all, but so many legitimately nice broodmares would be lost if we did so.

It is likely very relevant whether or not the foal is intended to be retained in the breeding program, or sold as a riding horse. I think most buyers for riding horses aren’t even aware of WFFS and won’t care if the horse is a carrier – but many breeders have WFFS on their radar now, and may not want a horse in their program that is a carrier. Particularly now that WFFS is becoming more difficult to avoid; there are tons of really nice stallions right now that are carriers.

This would be a good question for the DBG on FB. I think you’d get a lot of meaningful and thoughtful responses.

I’m a very small, small, breeder and tested the mare (negative) and bred to a WFFS carrier stallion. My plan was to not breed the resulting offspring anyway, so it didn’t bother me one bit to breed to this stallion.

I think there’s a pretty good idea that it doesn’t affect them, not significantly anyway. In all the deep dives that many countries did into trying to find the origin of this disease, in all the testing that’s been done including of so many horses who are out there currently competing, or who did compete at high levels in their teens, it just seems unlikely that many horses would be out there if it cause problems.

It may be something like HERDA, where carriers do have some structural changes to ligaments (maybe tendons, don’t quote me). That much is known. What’s not known is what impact that has on the horse, but all that I’ve ever seen on that is that it might be what has given the original, and subsequent offspring carriers, and advantage in the ring due to some extra “snap” to their movement - faster, quicker, etc. But that hasn’t been studied, and it’s only speculation.

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That’s my line of thinking.

Did you see this, thought it was interesting but obviously needs to be studied more in depth:

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That’s really interesting! And yes, much more research is needed. I can’t tell if the study is published yet and don’t have time right now to go searching for it, but I’d want to know if they chose study horses who are as unrelated as possible, since there are enough lines out there that reliably produce the same type of conformation and movement. And if that line happens to be a carrier, you can’t just say their movement equates to carrier status. Did I make sense?


This study was presented at ESS this year, and I sat in on the presentation. It was very much a pilot study; if I remember correctly, they used a herd of horses at just one barn for logistical reasons. The abstract is in JEVS. I don’t know where/when they intend to publish the full paper, but I’m sure Dr. Brooks would be more than happy to answer more specific questions about their protocol and plans.

It was a very interesting presentation.


Thanks for the correction, carrier vs positive-glad you understood what I was asking!