Presence of aflatoxin in corn not viewed as widespread

Traces of aflatoxin glow blueish white under a blacklight at Duffe Grain in Wilton in this photo taken in 2005. (Brian Ray/The Gazette)
Traces of aflatoxin glow blueish white under a blacklight at Duffe Grain in Wilton in this photo taken in 2005. (Brian Ray/The Gazette)

Grain elevators in Eastern Iowa are testing for the presence of a toxin in corn that could create another headache for farmers already dealing with the worst drought in 56 years.

Aflatoxin is harmful or potentially fatal to livestock and is considered cancer-causing to animals and humans. The naturally occurring toxin is the byproduct of a powdery, olive-green mold that has emerged in some Eastern Iowa corn fields.

While a farmer in southern Linn County has had corn rejected for aflatoxin at a level higher than 20 parts per billion, the maximum allowable for the food chain, that does not indicate the problem is widespread.

"I really haven't heard about too much and I was expecting more than I am hearing," said Jim Fawcett, Iowa State University Extension agronomist in Iowa City.

"I heard a lot about of aflatoxin when the first fields were harvested in southern Iowa. There was quite a lot in corn showing up at elevators in Eddyville."

At Duffe Grain in Wilton and West Liberty, grain merchandiser Kim Tyler said corn has been testing free of aflatoxin.

Aflatoxin is showing up in 2 percent to 3 percent of the corn arriving at River Valley Cooperative locations, according to Jim Gruenhagen, vice president of operations.


"We're probably a third of the way through the harvest, so I think this is kind of what it's going to be for the rest of the season," Gruenhagen said. "There are pockets, but it's not widespread."

In the Midwest, aflatoxin levels are highest during hot, dry summers. The prime conditions for the fungus to produce toxin are warm nights with temperatures above 70 degrees during the final stages of corn filling August and September in a period of drought.

The toxins are produced inside the corn kernels and their presence can be determined only by specific analytical tests. Because aflatoxin levels can vary greatly from kernel to kernel, sampling each load of corn before it is stored in a grain bin is a critical step to determine the actual level of aflatoxin.

Fawcett said farmers discovering the presence of aflatoxin while harvesting need to contact their crop insurance provider to document their potential loss. Once the grain is stored in a bin, it is no longer eligible for insurance coverage.

Fawcett and Gruenhagen said corn contaminated with aflatoxin can be used as feed by livestock producers as long as levels are less than:

  • 100 parts per billion for breeding beef cattle, swine and mature poultry
  • 200 parts per billion for finishing swine
  • 300 parts per billion for finishing cattle.

"There are cattle producers who would be interested in buying it at a discount," Gruenhagen said.

The U.S. Food and Drug Administration has approved allowing corn containing more than 20 parts per billion of aflatoxin to be blended with corn with lower levels or no aflatoxin for animal feed. Before doing any blending, grain dealers and the Iowa Department of Agriculture and Land Stewardship must sign a compliance agreement.

Each batch of blended corn must be analyzed to determine the aflatoxin level. The results of the tests must be provided to the livestock producer purchasing the blended corn.

The blended corn must be clearly identified and labeled for animal feed use only. Corn containing aflatoxin levels greater than 500 parts per billion cannot be blended.



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