Equine nutritionist Dr. Steve Jackson, shown here taking pasture samples while a foal looks on.

Equine nutritionist Dr. Steve Jackson, shown here taking pasture samples while a foal looks on.

Anne M. Eberhardt

Evidence Presented at Keeneland Suggests All Horses May Be at Risk

By Kimberly S. Graetz

The foal loss syndromes facing Kentucky's pregnant mares might be just the start of a host of problems that could affect horses of all ages, breeds, sexes, and uses in Kentucky and other states. Whether you have a gelding that is on turn-out, a yearling, suckling, stallion, or non-pregnant mare, there could be problems brewing. This information and much more was brought to light at an standing-room-only, open meeting at the Keeneland sale pavilion in Lexington, Ky., on the evening of May 10. The Kentucky Thoroughbred Farm Managers Club and the University of Kentucky brought together a panel of 10 experts to reveal what is known about the problems now facing Kentucky and other states to the north.

Included were the latest numbers from the University of Kentucky Disease Diagnostic Center and results from a survey of horse owners affected by the syndromes. The Diagnostic Lab reported on Thursday that a total of 386 aborted/stillborn equine fetuses/foals had been submitted for diagnostic testing/evaluation since the problem first arose late last month.

Dr. Roberta Dwyer of the University of Kentucky presented results of the survey sent to 270 farm managers,159 of which responded by Wednesday morning, May 9. The results show there were 37 farms that had no early fetal/foal loss, but 17 farms that had more than 50% loss. Dwyer reported there were 3,294 mares fitting the questionnaire criteria of having been checked in foal at 42 days. Of those, 2,616 were still in foal on May 8, for a 79% in-foal rate.

Zearalenone, a type of mycotoxin, was put forth as the possible cause of the recent rash of late-term stillbirths, critically ill foals, and early-term fetal loss. But while experts seem to be in agreement that it is a good possibility that zearalenone in particular is indicated, they aren't ruling out other possible causes or focusing on that one mycotoxin as the sole instigator of illness. Whatever the cause, the effects are cumulative, and they now are causing problems in horses other than broodmares.

"The whole equine population seems to be having insult. We're seeing illness in other genders and age groups," said Dr. Doug Byars, head of the medicine unit at Hagyard-Davidson-McGee veterinary firm in Lexington. He said clinics and farms are starting to see pericardial perfusions (pericarditis, or fluid around the heart) in adults and foals, eye problems in sucklings and yearlings, and lack of weight gain or weight loss in growing horses. One common symptom is general ill thrift.

Mycotoxins are known immunosuppressants. Because of that, Byars explained, this could be a threshold problem--meaning a horse could take in small doses over time until it gets to a point it can't handle the daily insults any longer. This could result in an increase in any number of problems--from fever to secondary infections to cancer.

Mycotoxin-binding agents used as feed additives are being recommended for horses of all ages. "They offer a window of hope," said Byars. The binding agents only take away the mycotoxins that are in the digestive tract; they don't have any known effect on toxins already circulating in the horse's body.

From research in other species, it is thought that reducing exposure to the mycotoxin (keeping horses off affected forages) and using the binding agent could result in a very dramatic reversal of clinical signs in a matter of days or less than a week, according to Dr. Kyle Newman, a nutritional microbiologist with Venture Laboratories in Lexington. "The insult is cumulative over time, but once you remove the source, you get a dramatic improvement," said Newman.

Among problems mycotoxins cause in other species of animals are depression in growth rate and compromise of sperm quality and motility, said Newman.

Dr. Steve Jackson, an equine nutrition consultant and owner of Bluegrass Equine Nutrition, said that a preliminary test result on samples of pasture taken last Thursday (May 3) for zearalenone showed 260 ppb (parts per billion). That is higher than expected, he said, adding that literature research revealed that 100-300 ppb have been shown to cause problems in other livestock. Byars added that he has recovered zearalenone from the urine of affected mares.

However, Jackson, Byars, and the other panelists emphasized that it would be a critical error to assume that the definitive answer is a mycotoxin, specifically zearalenone, at this point.

Despite that warning, among the information Jackson presented that points to a mycotoxin cause was decreased yearling growth data. (Mycotoxins are known to interfere with growth rates in other livestock.) "I noticed horses this spring were not responding to grass as they normally do," said Jackson. In looking at figures from regular weighing of a certain group of yearlings, he said that usual average daily weight gain in Kentucky is 1.6 pounds per day. This year, he saw 40% of the yearlings in the group were losing weight.

Jackson recommended not feeding this year's Kentucky hay to horses until more is known about the cause of the problems.

Tests are ongoing with samples of forages and fetuses in an attempt to come to a conclusion as to the cause or causes of the problems now facing Kentucky, Ohio, and potentially several other states. One veterinarian drove 7 1/2 hours from Northern Ohio to attend the meeting because the problem is there, he said (see related bloodhorse.com story).

The current recommendations for pregnant mares is to cover your bases, said Dr. Tom Riddle of Rood & Riddle Equine Hospital in Lexington. Riddle was the first veterinarian to focus on the early fetal loss problem. He recommends using domperidone and the mycotoxin binding agent feed additive to counteract the effects of mycotoxins, short-term banamine for fighting endotoxins, and sulfatrimethaprim and antibiotics in the case of secondary infections.

In response to a question from the audience about shipping horses out of state, horse owners were reminded that other states may be having the problem, and that the damage might already be done even if the horse leaves the area. Only time will tell.

Other panelists were Steve Johnson, president of the Kentucky Thoroughbred Farm Managers Club; Dr. Roger Murphy, president of the Kentucky Association of Equine Practitioners and the Kentucky Veterinary Medical Association; Dr. David Powell, an equine epidemiologist at the University of Kentucky's Gluck Equine Research Center; Dr. Lenn Harrison, Directory of the UK Livestock Disease Diagnostic Center; Dr. Roberta Dwyer, an expert in veterinary preventive medicine at the Gluck Center; Roger Allman, a pasture consultant and owner of The Farm Clinic in Lexington; and Fred Seitz, president of the Kentucky Thoroughbred Association/Kentucky Thoroughbred Owners and Breeders.