Aflatoxins Found In Some Northwest Iowa Corn

Iowa farmers in areas that were drought –stressed this summer should test for aflatoxin, ISU specialists advise.

Aflatoxins have been found in some 2007-crop corn in northwest Iowa, according to Iowa State University Extension field specialists. Farmers in areas that were drought-stressed this past summer are urged to test their cornfields and feed for its presence. ISU specialists made that announcement on September 27.

Aflatoxins are a group of chemicals produced by certain mold fungi and can be fatal to livestock. They also are considered carcinogenic to animals and humans.

"We have had a few positive tests for aflatoxin – not a lot yet, and hopefully it stays that way – but we have had a few samples of corn test positive for aflatoxin," says Joel DeJong, ISU Extension field agronomist in northwest Iowa.

DeJong says the production of aflatoxins is related to drought stress. Warm, dry periods are breeding grounds for the toxins. He hoped the rainfall in August would reduce that risk, but there have still been a few positive reports of the toxins occurring this year.

Only a few incidents reported so far

DeJong has heard of three reports from farmers who have confirmed aflatoxin in their fields, he says. The fields were in two counties in northwest Iowa – areas that saw very little rainfall through much of May through July. Also, the toxins were not widespread across those fields, he notes.

However, corn growers must test for the toxin before harvesting their crop, or it won't be covered through crop insurance.

"Crop insurance does not cover loss if it's not identified in the field," emphasizes DeJong. "So if you have all your corn harvested and haul it to the elevator and it tests positive for aflatoxin, your insurance will not cover losses identified at that time." Also, improper storage of corn increases the level of toxin present.

Cattle producers need to test feed

Those farmers with cattle in these affected areas should test their feeds for aflatoxin before giving them to their livestock, says Beth Doran, an ISU Extension beef field specialist, who works with the Iowa Beef Center. She says aflatoxins can reduce feed efficiency in cattle and reduce the reproductive capability in breeding cattle. And, while a less likely scenario, she says they may result in an animal's death.

Livestock operators need to know if and how much aflatoxins are present in their feed and how to address them. "It's cheaper to send it in and get a test on it than it is to lose an animal," says Doran.

The federal Food and Drug Administration has guidelines on what is an acceptable aflatoxin level in corn based on its intended use. Anything under 20 parts per billion (ppb) likely will return a negative test, says DeJong.

Follow testing, feeding guidelines

Corn intended for breeding beef cattle must have less than 100 ppb; for finishing cattle, less than 300 ppb; for young animals, less than 20 ppb; and for dairy cattle, less than 20 ppb.

For more information about aflatoxins, including how to prevent them, the consequences of high levels, testing methods and photos, review the publication Aflatoxins in Corn. This ISU Extension publication is available online at It also can be ordered through any ISU Extension county office or the ISU Extension Distribution Center by calling (515) 294-5247.

The Iowa Beef Center at Iowa State University was formed in 1996 by a legislative mandate. Its goal is to support the growth and vitality of the beef cattle industry in the state. As part of ISU Extension, the Beef Center also serves as a central access point for all ISU programs and research related to the beef industry. For more information visit

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