We all know not to feed moldy hay or grain. We also know that horses can be exquisitely sensitive to amounts of mold/fungal toxins that can’t be detected by appearance or odor, such as fumonisin or moldy-corn poisoning. However, your horse may be adversely affected by low concentrations of other mycotoxins as well.
Our chart on page 20 lists some mycotoxins and likely symptoms. In addition to the problems listed, feeding of mycotoxin-contaminated hay or grain may lead to decreased appetite, nonspecific intestinal problems — such as low-grade colic, diarrhea — and overall poor health.
Dangerous mycotoxins can be found on pastures, grains, straw and in hays, especially those with mature seed heads. Not surprisingly, a horse is more likely to eat a mold- infested grain mix than moldy hay, especially since molds in grains can be masked by molasses or processing like pelleting.
If you suspect a mycotoxin problem, contact your veterinarian immediately. Your best resource for testing and identification of the toxin is likely your state’s veterinary diagnostic laboratory, which your vet can help you contact. Free expert advice on what mycotoxins may be most likely involved in your case will also probably be available, so don’t hesitate to ask questions when you call.
The only real treatment for a mycotoxin-related problem is to stop feeding the contaminated pasture, hay or grain.
Some supportive therapies may be recommended for specific toxin-related problems, but in general recovery depends on providing a high-quality, adequately supplemented diet that is easily digestible. Extra antioxidant support in the form of B vitamins, especially, is usually helpful in these cases.
Mycotoxin binders are of no use once the animal becomes ill, although interest is growing on including mycotoxin binders in the diet in hopes of preventing these problems. You will see claims that various clays or aluminium and silica compounds can bind mycotoxins. However, there are often no studies to prove they actually have this effect inside the animal and certainly none specifically related to the horse. Note: The FDA maintains the position that the inclusion of aluminosilicate and hydrated sodium calcium aluminosilicate clays in animal feeds can’t be claimed to protect from mycotoxin because studies to support the claim haven’t been submitted.
With some mycotoxins in other species, use of this type of binder can actually make the situation worse. A recent study showed that the montmorillonite clays used as a mycotoxin binder enhanced the toxicity of zearalenone in mice. They can also interfere with mineral absorption and, if they do bind, some toxins may release them again depending on the pH in the gut.
Veterinarians sometimes recommend other approaches, including Alltech’s Bio-Mos. This is a complex plant polysaccharide derived from the cell wall of the yeast Saccharomyces cerevisiae, which is both an immune stimulant and a bacterial toxin binder.
Most of the research on Bio-Mos has been in food-producing animals, but it’s gaining in popularity as a supplement for foal and weanling digestive disorders.
Alltech also makes a variation of Bio-Mos specifically designed and patented as a mycotoxin binder called MTB-100 or Mycosorb. It also has a mannanoligosaccharide base. MTB-100 is said to have eight times the mycotoxin binding capacity of clays. Triple Crown Feeds have MTB-100 and Bio-Mos added. Although these compounds have been extensively evaluated by the company, they are not FDA-approved as mycotoxin binders for horses either.