Mycotoxins and Metabolic Stress in Equine Athletes

Thanks to climate change and increasing amounts of grain blends, the prevalence of feed-borne mycotoxins (dangerous toxins exuded from molds) is on the rise, according to Trevor Smith, PhD, of the University of Guelph, Canada. Smith, a professor with a research interest in feed and food toxicology, discussed the effects of one of the most common families of mycotoxins--Fusarium--on horses at the Veterinary Sport Horse Symposium, held Sept. 22-24 in Lexington, Ky.

Smith described two studies performed at Guelph by Susan Raymond, a PhD student in his lab: The first involved feeding a group of 12 mature, nonexercising mares grains contaminated with Fusarium mycotoxins, along with feeding a control group of 12 similar mares grain without contamination. The researchers measured the horses' grain concentrate intake every seven days for three weeks and they noted decreased consumption among the mycotoxin-fed horses at each time point, compared to the control animals. In the second study researchers evaluated the same diet in 12 mares, but they added exercise to the horses' routine. Researchers still witnessed a decline in concentrate consumption, but it was not as severe because the exercise increased the horses' energy requirements and forced them to eat. Weight loss was recorded in this study, whereas it was not in the study of nonexercising mares.

"Feeding grains contaminated with Fusarium mycotoxins can alter the metabolism and reduce performance," Smith concluded. "This can lead to financial losses for producers."

Types of Fusarium mycotoxins and their effects include:

The Fumonisins The neurologic syndrome equine leukoencephalomalacia (ELEM), ataxia, and sudden death can result.

The Trichothecenes can cause hemorrhaging and ulcers and make animals susceptible to secondary mycotoxic diseases.

Zearalenone causes enlargement of the uterus, rectal and vaginal prolapse, abortion, and infertility.

Fusaric Acid causes a drop in blood pressure, reduces feed consumption, causes lethargy and loss of muscle coordination, and increases brain concentrations of serotonin and tryptophan.

Methods to minimize or prevent mycotoxicosis include using:

  • Processing methods such as cleaning grain (removing screenings);
  • Mold inhibitors such as propionic acid (which lowers pH level of stored grain);
  • Supplementing enzymes;
  • Mycotoxin adsorbents (which bind the mycotoxins) such as glucomannan polymer extracted from yeast cell wall; andP
  • hysical treatments such as heat, which destroys live mold spores.

While Smith admitted we can't prevent the consumption of all mycotoxins, he noted that an appropriate adsorbent can be used as a prevention method.

About the Author

Alexandra Beckstett, The Horse Managing Editor

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.

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