Preliminary Test Results Suggest Possible Causes, Preventative Measures

After testing numerous pasture samples for mycotoxins, endophytes, and other possible causes to the problems in Kentucky, tests have shown higher than expected levels of a mycotoxin called zearalenone, according to Dr. Steve Jackson, a consultant for Bluegrass Equine Nutrition. Jackson was one of the presenters at the Late Term Abortions and Early Fetal Loss Information Session at the Keeneland Sales pavilion Thursday. Jackson and other presenters stressed that zearalenone has not been pinpointed as the definitive cause to the problems; however treating the higher levels of zearalenone could help in the long run.

Zearalenone has known estrogenic properties (causes estrus) and can cause infertility and abortions in horses. Researchers are investigating whether zearalenone and other mycotoxins were released in the grass as a result of unusual spring weather patterns in Central Kentucky. The levels of zearalenone found were at 260 parts per billion (ppb). He said that ranges between 100-300 ppb could create adverse reactions in livestock. In addition, Dr. Doug Byars of Hagyard-Davidson-McGee said that zearalenone has also been found in mares' urine. The mycotoxin zearalenone is produced by the fusarian molds which are produced in more temperate climates and usually appear later in the year. Dr. Kyle Newman, a nutritional microbiologist for Venture Laboratories in Lexington referred to the dry rain-deprived Kentucky pastures as looking more like August than early May.

Jackson recommended that horse owners treat mares, and other horses, as if they have had mycotoxin exposure while researchers continue attempts to pinpoint the definite cause of the problems. Treatment would be to give horses feed containing a mycotoxin binder feed additive. Mycotoxin binders help the horse's digestive system to absorb any mycotoxins that might have been ingested or are already in the gut. This would eliminate the mycotoxin load from the horse's system. Effects should be immediate, and the additive ends up costing only 30 cents per day. Jackson stressed that mycotoxin binders do not reverse any damage already done, but can prevent further problems. "It's a do no harm situation," he said. "It is totally innocuous. There is no down side to doing this. However, it would be a critical error to think that we have the definitive solution."

A mycotoxin binder produced by Kentucky-based Alltech is available through Farmers Feed Mill/Hallway Feeds, Southern States, McCauley's, and Brumfield Feeds. Another product known to be a mycotoxin binder is alfalfa meal. The panel of speakers agreed that limiting access to pasture would reduce exposure to any mycotoxins or other problem agents. Additionally, hay harvested this year has the potential to cause problems, so presenters encourage farms to avoid feeding this hay.

Dr. Jimmy Henning, an Extension Forage Specialist at the University of Kentucky's College of Agriculture, and Roger Allman, a pasture consultant for The Farm Clinic covered some of the other possible causes for the syndromes. These causes include an abnormal reaction of tall fescue to environmental factors. Testing for endophyte levels in fescue is not always conclusive, however. "No one has measured the parts per billion, or how much (endophyte) it takes to cause the mares to have this difficulty," Henning explained. Other possible toxins include a new endophyte that might appear in bluegrasses or orchard grasses; a fungus on early seed heads; or white clover which might have become naturally toxic with cyanide during the frost and subsequent drought. Henning believes these are highly unlikely culprits.

Allman has been collecting species-specific forage samples daily and sending them to testing labs. These include bluegrass, orchard grass, tall fescue, clover, and other native grasses. He's been collecting forage samples from as many management levels as possible. He's comparing old to new pastures, pastures that are fertilized at different times, and those that have varying amounts of fescue and clover.

Researchers continue to explore every possible cause for the mysterious syndromes and at this time are unable to give any set answers. New test results will be reported on as they emerge. Allman remains cautious in his estimations. "I've heard contradictions to every theory that I've heard postulated," he said, "I don't plan to speculate or make recommendations without hard data."

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