We all strive to provide our horses with the most wholesome foods possible, but mycotoxins are always a threat. Mycotoxins are toxins/poisons produced by mold contaminating grains, seeds and even hays, pasture or straw. They can cause problems in very small amounts, and what you feed your horse may look fine to the naked eye.
The mycotoxicosis (mycotoxin-induced disease) most familiar to horse owners is leukoencephalomalacia, ?moldy-corn poisoning.? In this disease, the horse's brain literally liquifies and by the time the horse is obviously ill it will be fatal and irreversible. Moldy-corn poisoning is caused by the mycotoxin fumonisin.
Dangerous in amounts of only 1/40th of fumonisin, aflatoxin is the fungal toxin behind the huge recall of feeds on the East Coast a few years ago. Symptoms of high-level exposure include liquifaction of the brain, fat degeneration, liver damage, damage to the intestinal tract with hemorrhage, depletion of lymphocytes (a type of white blood cell) and heart damage.
Potentially equally dangerous is T-2 toxin, causes intestinal damage, skin changes and altered immune system. Complicating the task of assigning safe upper limits for intakes of these toxins is that there is often more than one toxin in a contaminated feed. This makes it impossible to determine whether one is the culprit or if it is a combined effect of the mixture. In addition to the effects already described, negative effects on reproductive function may occur.
Low-level intake of mycotoxins, adding up to a longer term, chronic exposure, can also be harmful, but the effects only begin to be obvious over several weeks or so. These may include:
- Weight loss
- Dull coat
- Skin problems
- Performance issues
- Changes in urine/urination
- Behavior changes
- Possible colic
One clue that you're dealing with a feed-related issue is that more than one horse will be showing symptoms, although not necessarily to the same degree. If a mycotoxin problem is suspected, blood should be sent for a chemistry screen.
Binders and Inactivators.
There are two basic categories of products that decrease the threat of mycotoxins: adsorbents and biological modifiers. Adsorbents bind the mycotoxins to their surface so that they can't damage the intestine or be absorbed. This includes several different clays and zeolites.
From data in other species, to be effective, they must be consumed at a rate of approximately 1 to 2% of the diet. An average horse consuming 10 kg of food per day would need to eat 100 grams (3.5 ounces) per day as a minimum. Charcoal is also an effective adsorbent. Saccharomyces yeast can also be given to adsorb mycotoxins.
There is no universally effective adsorbent. The activity of clays and zeolites depends on the pH and also the type of mycotoxin. Fortunately, aflatoxin is effectively adsorbed by a wide variety of adsorbents. The Saccharomyces yeast cell wall has a wide activity.
Although mycotoxins may be present on hays, especially clover, ryegrass or fescue, hay isn?t a major source for horses and avoiding those hay types solves that problem. Damaged grains, processed grains, and seed meals are the most likely to be contaminated with mycotoxins, especially the fines at the bottom of the bag.
You can minimize your horse's risk by feeding high quality whole grains (never feed the ?fines?/broken pieces at the bottom of a bag) and learning how to read the date tags on bagged commercial grains. Avoid grain mixes that are over three months old.
Digestive upsets can be a sign of mycotoxin intakes and can put the horse at higher risk of effects from mycotoxins. Supplementation with Saccharomyces cerevisiae yeast (Yea Sacc) may help, since this strain?s cell wall can adsorb mycotoxins. However, it isn?t known if it also can biologically inactivate them. The dose for an anti-mycotoxin effect is unknown, but the digestive-enhancing dose is 46 billion organisms/day.
Several supplements are available that claim to deal with toxins in feed, including mycotoxin. Only clays and charcoal are currently available. Feeding high levels of charcoal or clay long-term can block the absorption of key nutrients, but it's fine short-term.
Durvet?s activated charcoal gel is a first-aid product we think all barns should have on hand. it's highly effective and also works for accidental drug overdoses, any suspected poisoning and even grain overload situations. We like VivoZeolite for short-term protection.
Article by Eleanor Kellon, VMD, our Veterniary Editor.