FAQs: An Interview With Dr. Doug Byars on Excessive Foal Loss

Interview with Dr. Doug Byars, DVM, Dipl. ACVIM, Dipl. ACVECC, head of the Kentucky-based Hagyard-Davidson-McGee veterinary firm's Medicine Unit in Lexington that includes neonatal intensive care.

Of his comments, Byars said, "For all of these following recommendations, we don't know if they are useful or futile because we don't know when the 'hammer' hits these horses. Whatever you do hopefully helps prevent the problems. We don't know if there are any therapeutic benefits. All of my comments are being pointed toward the culprit being grasses. We haven't found an infectious disease. There are syndromes in other species of animals related to toxins or endophytes that relate to what we are seeing in the horses. The increased activity this problem has created has made it difficult for us to get together to discuss the problem, but we are mobilizing and getting a lot of input from institutions and toxicology places. We hope to get a definitive answer in the near future."

1) What can a horse owner/farm manager do today to protect his pregnant mares?
A. Monitor all foaling mares. Treat every foaling mare as being at high risk. Medicate them as your vet recommends (including domperidone and ancillary treatments such as antibiotics).

B. For early pregnancies, ultrasound pregnant mares as recommended by your veterinarian. Some vets say ultrasound them daily, but what can you change if you find out she has aborted or is aborting? If you've ultrasounded and find mares that are empty, your vet may recommend subjective treatment for the remaining pregnant mares, including hormones such as progesterone. Other checks of pregnant mares should be up to your veterinarian's preference.

C. Mow pastures; top them down to get rid of grasses present during the drought. Now that we've been fortunate enough to get a little rain, it might change things.

D. Adjust feeding management. Make sure hay is available in the fields when mares are turned out, and make sure it is good-quality hay.

2) Should mares be moved out of Kentucky?
My current recommendation is that foaling mares are high-risk shippers, so most shouldn't be moved. Also, we don't know if other states are having similar problems. In other states east of the Mississippi, we are hearing people comparing their problems to ours at this point, but we haven't gotten anything definitive. Where you would move them to would be questionable. There is no question we have a problem here, but here the density of our horses would allow us to more readily see a pattern. That might not happen in places where there are not so many horses in one place. We are waiting for reports from other areas to see if there are inordinate amounts of early fetal losses or red bag foalings. We have indications that other states may be involved in this problem. Those indications are only from vets who call here and say they had red bag foal. One foal isn't enough to tell them yes. Everything else is rumor at this time.

3) If a previously pregnant mare is scanned not in foal, can she be re-bred this year? Will there be complications for next year?
She can be re-bred this year assuming you can get her cycling again, get back to the shed, and she cultures negative. Will there be complications for next year? No one can say. For this year, if a manager can "knock out" endometrial cups and she cultures clean, then you can get her back to the shed. Your attending vet will have recommendations for individual mares. Also, it's a management call because mares might "shut down" and by the time we could get them to cycle, it will be too late in the season. It might be better to leave them open this year and move them up to a February cover next year.

4) If a pregnant mare foals and the foal dies from the syndrome, can she be re-bred this year? Will there be complications for next year?
It's pretty much the same answer as before. If she cultures clean and you can get her to cycle, there's no reason not to breed her this year.

5) If a mare delivers a stillborn foal, the foal dies, or she aborts a fetus, what should be done with the foal/placenta?
You should submit it to the appropriate diagnostic center. (In Kentucky, that's the Livestock Disease Diagnostic Center on Newtown Pike in Lexington.)

6) If a mare either is not pregnant or delivered a live, healthy foal and was not re-bred before now, how should she be managed?
There is no change in management for non-pregnant mares. Breed her the same as usual. She may be at some advantage if she is bred now because if we had a problem with grasses and they've been mown, then we might get rid of problem by the time she is pregnant.