Mycotoxins in Grains and Animal Feeds
Martin W. Adams, PAS – Equine Nutritionist for Southern States
Mycotoxins are toxins produced by molds that can affect the health of animals in many ways. These mycotoxins can be present in hay, pasture and grain. Mycotoxins are stable chemical compounds, they are resistant to heating and can remain in the feed for an extended period of time
Aflatoxin - a carcinogenic fungal toxin produced in improperly stored or damaged feeds. The two molds that produce aflatoxin are Aspergillus flavus and Aspergillus parasiticus. Aflatoxin B1 is the most toxic and common, followed by G1, B2 and G2. Their toxins can be produced pre-harvest in the field and post-harvest in storage. In both cases, damage from insects, mishandling or weather stress will help the fungi invade the seed. While aflatoxin is most common in warm, dry areas, these molds can attack crops in northern climates if conditions are favorable. In addition to cereal grains, soybeans, rice and peanuts, aflatoxin can occur in silage and hay can occur. The prime cause of aflatoxin is moisture, so proper harvesting, drying and storage are important factors in lessening contamination and toxin production. Acetic and propionic salts are highly effective in inhibiting mold growth, thus greatly decreasing the incidence of aflatoxin production. In mares, aflatoxin decreases reproductive performance, increases embryonic death rate and causes birth defects.
DON (Deoxynivalenol) or Vomitoxin - a toxin produced by several species of Fusarium molds, and they are the most common molds found in hay and feed grains. Swine are very sensitive to this toxin, which causes vomiting, feed refusal, immune suppression, diarrhea, weight loss and milk production loss in pigs and other animal species. Horses appear to be sensitive to this toxin also, DON is implicated in colic and reduced feed intake in horses.
T-2 Toxin - a toxin produced by certain species of Fusarium molds, mainly Fursarium sporptrichioides. T-2 Toxin causes both acute and chronic symptoms in most species of livestock. Symptoms of toxicity include diarrhea, irregular heart rate, scarring of the digestive tract, and rapid eye blinking.
Ochratoxin - toxins produced by Aspergillus ochraceus and Pencillium viridicatum. While ochratoxin refers to a family of compounds, only ochratoxin A occurs naturally and is of toxicological significance. Ochratoxin A is a nephrotoxin (causes kidney damage) and is known to suppress immune system function. Ochratoxin A is found mainly in corn, barley, wheat and milo.
Zearalenone - a toxin produced by several species of Fusarium molds. Its chemical structure is similar to the female sex hormone estrogen and can impair reproductive function in many species. Zearalenone is known to cause reproductive disorders in livestock, especially swine.
Fumonisin - toxins produced by two Fusarium molds, Fusarium moniliforme and Fusarium proliferatum. There are at least six fumonisins that have been isolated: A1, A2, B1, B2, B3 and B4. Fumonisins are found mainly in corn and corn-based products. These mycotoxins can impair immune function, cause kidney and liver damage, and result in decreased animal performance and cause death. Corn screenings appear to be a source of high levels of fumonisin. Fumonisin B1 is responsible for equine leukoencephalomalacia (ELEM), also called moldy corn poisoning. In swine, fumonisin B1 has been implicated as the cause of porcine pulmonary edema (PPE). And in humans, fumonisin B1 has been linked to esophageal cancer. A maximum level in animal feeds has been set by the Food and Drug Association (FDA).
The FDA can support enforcement action against interstate shipments of corn exceeding these levels of aflatoxin.
| Aflatoxin Contamination - Levels of Concern for Corn |
| Human Food |
20 ppb |
| Feed for immature livestock and poultry |
20 ppb |
| Feed for dairy cattle |
20 ppb |
| Breeding cattle |
100 ppb |
| Breeding swine |
100 ppb |
| Mature poultry |
100 ppb |
| Finishing swine (100 pounds or more) |
200 ppb |
| Finishing beef cattle |
300 ppb |
The FDA has established these levels in animal feeds for total fumonisin levels.
| Fumonisin - Levels of Concern |
| Horses and rabbits |
5 ppm (no more than 20% of diet) |
| Swine and catfish |
10 ppm (no more than 50% of diet) |
| Breeding ruminants and poultry |
30 ppm (no more than 50% of diet) |
| Ruminants (3 months or older) |
60 ppm (no more than 50% of diet) |
| Ruminants (3 months or older) |
60 ppm (no more than 50% of diet) |
The FDA recommends these limits for DON.
| Vomitoxin or DON - Levels of Concern |
| Human Food |
1 ppm |
| Ruminating Beef Cattle |
10 ppm in (50% of diet or 5 ppm in total diet) |
| Feedlot Beef Cattle |
10 ppm in (50% of diet or 5 ppm in total diet) |
| Mature Beef Cattle and Chickens |
10 ppm in (50% of diet or 5 ppm in total diet) |
| Swine |
5 ppm in (20% of diet or 1 ppm in total diet) |
| Horses and other animals |
5 ppm in (40% of diet or 2 ppm in total diet) |
Ochratoxin, T-2 Toxin and Zearalenone - Levels of Concern -
There are no regulatory levels set for ochratoxin, T-2 toxin or zearalenone.
Southern States has a current policy that tests for aflatoxin and fumonisin in corn and corn byproduct feed ingredients, and for DON in wheat and wheat byproduct feed ingredients. Feed ingredients purchased by Southern States with detectable levels of mycotoxins are not used in horse feeds or other animal feeds.
Southern States incorporates MTB-100 into The Triple Crown line of horse feeds and supplements. MTB-100 is an esterified glucomannan product derived from yeast cell walls that has been shown to bind certain mycotoxins in the digestive tract and prevent their absorption into the bloodstream.
Roemer Laboratories (314-583-8600) can perform analysis on hay and grain samples for many mycotoxins including Aflatoxin B1, Fumonisin B1, DON, T-2 Toxin, Zearalenone and Ochratoxin.