Mycotoxins in Horse Feeds

What are Mycotoxins?

Mycotoxins are compounds produced in grains by specific molds or fungi. High moisture content of some grains and high ambient temperatures promote growth of mold and thus, mycotoxin production. Weather has a major impact on the levels of mycotoxins found in grains and grain-derived ingredients. It is not possible to find grain-based ingredients with ZERO mycotoxin levels. Further, even pastures and hay can have detectable levels of mycotoxins, as many molds are found in the soil.

The key is to keep mycotoxin levels within safe limits by screening incoming ingredients. We must formulate feeds so that higher-risk ingredients are used at lower, safer inclusion rates.

The Center for Veterinary Medicine (CVM) within the FDA focuses on 5 major mycotoxins in the U.S. and sets regulatory limits for both ingredients and finished feeds. Those mycotoxins are:

  • aflatoxins
  • fumonisins
  • vomitoxin (DON)
  • ochratoxin A
  • zearalenone

The first three mycotoxins are the ones of major concern in horses. Especially important is fumonisin, as it can cause “moldy-corn” poisoning (equine leukoencephalomalacia) which can be fatal. Luckily, harmful levels of fumonisin are seldom seen, but caution should be exercised when corn is harvested during drought and hot weather conditions.

Vomitoxin or DON is quite commonly found in many grains like corn, wheat, barley and oats and by-products made from these grains, like wheat middlings and distillers dried grains with solubles (DDGS). Luckily, the main negative effect of higher levels of DON is feed refusal – the horse won’t eat the contaminated feed – nice safety net!

Our Approach to Feed Safety with Respect to Mycotoxins

To ensure safety of our products, Tribute® Equine Nutrition tests incoming, higher-risk ingredients for mycotoxins. If tests show higher than allowable levels, the load is refused.

Wheat middlings (“midds”) result as a co-product from milling wheat. It is very commonly used in animal feeds as a source of protein and calories. Midds are also “sticky” and help hold pelleted feeds together, but will contain varying levels of mycotoxins and need to be monitored.

DDGS is produced when corn is used in a distillation process to produce alcohol or ethanol.  It is an economical source of protein, fat and phosphorous, and is relatively low in sugar and starch.

Unfortunately, the distillation process will concentrate the mycotoxin levels such that DDGS will be higher in mycotoxins than the corn from which it was made. This is why DDGS are not used in the Tribute® Superior Equine Nutrition feed line.  

For further protection, Tribute® Equine Nutrition products are formulated with a mycotoxin binder which can help render mycotoxins less harmful. Notably, forage can be a major source of mycotoxins in the horses diet and mycotoxin binders in feed help offset this risk, as well. All Tribute® Equine Nutrition products contain Equi-Ferm XL, a live proprietary yeast and prebiotics, which help alleviate the negative effects of mycotoxins in horses.


Maintaining zero levels of mycotoxins is not possible in animal feeds. In fact, all companies will have some level of mycotoxins in their products – the key is to keep those levels low enough to meet FDA/CVM safety standards. The ingredients going into Tribute® Equine Nutrition products are tested to make sure they are safe for the animals consuming them. Tribute® Equine Nutrition stands behind the entire product line with regards to safety and their intended use.

Article By: Nicole Rambo, Ph.D.
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