The Mycotoxin Alarm

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Mycotoxins are poisons created by molds and fungi. While they're all around us, they become of concern when they get into our horses? feed or bedding, especially straw bedding.

The weather can be a big factor in the development of mycotoxins in feeds. Wet years lead to some types of mold growth and drought years lead to others. Both conditions stress plants, lowering the plants? defenses against these invaders. Certainly the drought over many areas of the West and Midwest this year will contribute to mycotoxin levels in some feeds. Does that mean you should be on guard'

First, it's important to realize that mycotoxins are almost always present to some degree. Horses can handle small amounts on their own, but large amounts can lead to appetite loss, illness and even death. Depending on the exact toxin, it may develop right in or on the plant or grow after the feeds have been harvested and while they are being stored.

Mycotoxins can grow in grasses (think fescue and ergot poisoning for pregnant mares), but most cases of mold illnesses are associated with corn. Aflatoxin, noted in many pet-food recalls in recent years, is often the culprit. Other mycotoxins include fumonisin, zearalone, T-2 and DON (deoxynivalenol).

Horses will often refuse to eat moldy feed, especially hay. That hay is often dusty as well and the flakes won?t separate easily?both signals that something isn?t right. Unfortunately, if your horse is hungry enough, he'll eat the bad hay. And many horses, food hounds that they are, don't even look twice at grain with mold and mycotoxins.

You can check your feeds in a number of ways by yourself, but the only definitive way to rule mycotoxins in or out is to do laboratory tests. Those tests can also tell you if the mycotoxin level is dangerous.

Exam your hay carefully. The flakes should separate easily and not be dusty. Mold can sometimes be seen. The hay will smell moldy as well (don't inhale a bunch of the moldy spores or dust yourself!).

With grain, look for dustiness, funky coloring and clumping of the grain. Again, the smell may be ?off.? Be aware that the grain at the top of the bag may be fine, but as you work your way down, grain may be moldy. Ideally, the grains are separate and shift easily through your fingers.

Store your feed carefully. If the grain gets wet, discard it. Also, toss moldy hay bales, too (right out of the barn).

Feed manufacturers have multiple ways of checking their grain deliveries. If the ?test weight? of a sample of grain, say corn, is below the normal average, many feed mills will send out mycotoxin tests.? The lower weight is indicative of stressed plants. Some feed manufacturers also send representatives out to look at the fields where their grain will be harvested. Mold can sometimes be seen growing on the plants themselves or the plants may appear stunted.

SYMPTOMS.? What do you look for if you suspect mycotoxins causing problems with your horses' Multiple horses are generally ?off feed.? That could lead to weight loss and a dull coat. You may notice colic, skin problems or performance and behavior troubles. Deadly amounts of mycotoxin ingestion can lead to ELEM or equine leukoencephalomalacia. In these cases your horse's brain literally liquefies, and most horses will die. The mycotoxins aflatoxin and fumonisin are the most likely causes of this fatal syndrome.

BOTTOM LINE. Realistically, many feeds will have at least a low level of some mycotoxins this year, especially with the drought stress. Your feed manufacturer might even include binders to tie up the toxins as a routine additive to their mixes. Saccharomyces yeast cell walls can adsorb these toxins as can activated charcoal. Glucomannan supplements have also been shown to be beneficial. (See first-aid sidebar first aid sidebar.)

Article by Dr. Deb Eldredge, Contributing Veterinary Editor.