Dairy Farmers Warned to Check Feeds for Aflatoxin

Dallas, TX — Texas milk marketing cooperatives recently dumped several tanker loads of milk contaminated with aflatoxin, a toxic by-product of the mold fungus Aspergillus. “Some of this year’s feed corn contained aflatoxins and was fed to dairy cows,” according to Dr. Ellen Jordan, Extension dairy specialist in Dallas. “Lactating animals excrete aflatoxins into their milk.

“Fortunately, routine testing at every level prevents this milk from getting to consumers. Government regulations require milk to be free of aflatoxin. This contaminant can be detected at extremely minute levels so there is no risk to the public. Federal regulations are stringent on milk for obvious reasons.

Gene Wright, Assistant Director of the Milk and Dairy Division for the Texas Department of Health, said, “It’s much better with no milk dumped in the last two weeks, but before that we had our hands full.” Wright said this is the first bad year for milk contamination since 1988. “But dairies are becoming aware now of the problem and monitoring their feed more carefully,” he said.

“A tanker of milk represents a major financial loss to dairy producers,” said Max Sudweeks, Extension dairy specialist in Overton. “Tankers range from 45,000 to 55,000 pound in capacity. Depending on its size, a tanker of milk can be worth more than $7,000.”

Contaminated grains and grain by-products are the most common sources of aflatoxins in Texas. Corn silage may also be a source of aflatoxins, because the ensiling process does not destroy the toxins already present in silage.

Feed can be analyzed for aflatoxin and other mycotoxins at the Texas Veterinary Medical Diagnostic Laboratory in College Station or by a commercial laboratory.

Aflatoxicosis is typically a herd rather than an individual animal problem. If aflatoxin is suspected, the ration should be analyzed immediately. If aflatoxins are found, the source should be eliminated at once.

“Aflatoxicosis can be prevented only by feeding rations free of aflatoxin,” said Jordan. “Preventing aflatoxin contamination requires ongoing and thorough sampling and testing. First, buy from a reputable feed company and then closely monitor conditions on your farm that might contribute to aflatoxin development in stored feed. Moist and warm conditions can be dangerous.”

In dairy cattle, aflatoxin metabolites appear in the milk before any other signs develop. Dairy and beef cattle are more susceptible to aflatoxicosis than sheep. Young animals of all species are more susceptible to the effects of aflatoxins than mature animals. Pregnant and growing animals are less susceptible than young animals but more susceptible than mature animals.

Feed refusal, reduced growth rate, decreased milk production and decreased feed efficiency are the predominant signs of chronic aflatoxin poisoning. Aflatoxicosis also may impair reproductive efficiency and immune response, as well as increase susceptibility to other diseases.

Aflatoxins are metabolized in ruminant animals by the liver and excreted in the bile. Aflatoxin B1 is the most potent mycotoxin (toxic substance produced by a mold). This toxin increases the apparent protein requirement of cattle and is a potent cancer causing agent (carcinogen). When significant amounts of aflatoxin B1 are consumed, its M1 metabolite appears in the milk within 12 hours. Research suggests M1 is not as carcinogenic or mutagenic as is B1, but it does appear to be just as toxic as its parent compound.

Jordan and Sudweeks have developed a fact sheet for dairy producers with tips on how to guard against this mycotoxin from contaminating their herds. The fact sheet is available through county Extension offices.

-30-

Note: Texas Veterinary Medical Diagnostic Laboratory P.O. Drawer 3040 College Station, TX 77841-3040 Phone: 979/845-3414

To Texas A&M Agriculture News Home Page