A mare and her healthy foal in a paddock on a Lexington farm. May 9, 2001

Photo by anne M. Eberhardt

A mare and her healthy foal in a paddock on a Lexington farm. May 9, 2001 Photo by anne M. Eberhardt

Anne M. Eberhardt

Feed Additive Might Help Protect Mares During Foal Loss Syndrome

By Kimberly S. Graetz and Christy West

Veterinary and diagnostic professionals in Kentucky are working feverishly to identify the cause of the recent abortion and early fetal loss syndromes. One of the most probable causes is mycotoxins in pastures. If that is the case, then a mycotoxin binder used for other animals--and now being produced locally as a feed additive for horses--could offer the first preventative treatment for the current situation.

"If the problem is a fungus toxin, then the Farmers Feed Mill/Hallway Feeds additive could offer a product with scientific credibility and a high degree of safety," said Doug Byars, DVM, Dipl. ACVIM, Dipl. ACVECC, head of the Kentucky-based Hagyard-Davidson-McGee veterinary firm's Medicine Unit in Lexington. He cautioned that at this stage, however, it isn't known if the damage to pregnancies is already done and the therapy is too late.

"But, if we're right (about the mycotoxins), we are approaching this problem from a therapeutic standpoint for the first time, and that's good news," said Byars.

The feed additive, called Mare-Guard, uses a glucomannon product that is obtained in the processing of yeast. "It is a portion of the yeast cell," explained Lee Hall, vice president of Farmers Feed Mill/Hallway Feeds. Hall said the product is made by Kentucky-based Alltech, and that his company is purchasing the ingredient and making a feed supplement for mares. The product is used in other animals (including cattle, swine, and poultry) to bind the toxins in the animal's system and help the animal expel it rather than absorb it from the intestinal tract.

Hall said that Byars of Haygard-Davidson-McGee and Dr. Bill Bernard of Rood and Riddle Equine Hospital thought there was a good chance that this type of product could be useful in the current situation. His company rose to the task and began manufacturing the feed supplement, and it became available as of 3 p.m. Tuesday, May 8. He said several farms already have the additive and are using it; several others have orders in and are just awaiting processing and delivery.

"We're not promising a silver bullet," said Hall. "We're not sure anyone can preserve a pregnancy using this product. We just hope it can provide relief if the mares have these toxins."

Mare-Guard is being recommended to be fed at a rate of one pound a day per mare. Cost of the product is about 30 cents per mare per day. (For more information on this supplement, talk to your veterinarian or call Hallway Feeds at 859/255-7602.)

What Are Mycotoxins?
On April 25-28, Alltech presented its fourth annual seminar on the feed industry in Lexington. Included in that seminar was a presentation by Trevor Smith, BSc, MSc, PhD, of the University of Guelph. In his talk, he explained that mycotoxins are toxins produced by molds that can be toxic when consumed "in significant amounts" by livestock.

Mycotoxin binders are large molecular weight polymers designed to bind to mycotoxins in the animal's digestive tract, keeping those toxins from being absorbed and passing out harmlessly in the feces, explained Smith. The intended effect is to reduce the amount of toxin absorbed from the feed to the point that it does not affect the animal. The main challenge with mycotoxin binders is finding one that binds several toxins effectively while fed at low levels (if fed at high levels, the binder dilutes the nutrient density of the diet).

One of the best-known mycotoxins is the one produced by endophyte-infected fescue grass. (For more on fescue toxicosis see http://www.thehorse.com/0007/fescue_toxicosis0007.html.) Fescue toxicosis can cause late-term abortions, dystocia (difficult birth), agalactia (little or no milk production), a thickened or tough placenta, and/or extended gestational period.

In addition to the mycotoxins found in endophyte-infected fescue grass, many mycotoxins are produced in forages by Fusarium molds. The most important Fusarium mycotoxins in horse production are the fumonisins. Fumonisins cause equine leukoencephalomalacia, a disease characterized by an atrophy of the brain that results in loss of muscle coordination and death (for more information see www.thehorse.com/news/index021299.html). Fusarium molds can also produce zearalenone.  This toxin has estrogenic properties and can cause infertility and abortions in horses.  The trichothecenes are a group of Fusarium mycotoxins that include vomitoxin (DON). DON can cause loss of appetite, loss of muscle coordination, lethargy, bleeding in the intestinal tract and immunosuppression.  Another Fusarium mycotoxin is fusaric acid.  This toxin reduces blood pressure and therefore can interfere with functioning of the lungs and blood supply to reproductive organs in the mare.  It has also been reported that toxicity of Fusarium mycotoxins increases when combinations of toxins are found in feedstuffs.

These fungal toxins are only produced at certain stages of mold growth, and are often resistant to chemical or thermal treatments for destroying mold spores. The problem in Kentucky is thought to have stemmed from a particular environmental scenario. The state experienced a warm spring, followed by a hard freeze, then a drought. Since freezes and drought stress are known to increase fungal penetration of feedstuffs, conditions have encouraged fungal growth in Kentucky this spring.

There is some misinformation being passed around the industry regarding mycotoxin binders. Hall notes that brewers yeast and soybean hulls will not help bind toxins.