The discovery of aflatoxin in some of the drought-affected corn being harvested this year and the possibility of the growth of other toxic substances in grain that's in storage was recently reviewed by grain quality, plant pathology, and livestock feeding specialists at Iowa State University.
As a result of the tests for aflatoxin conducted by elevators in Illinois, Iowa, Indiana, Nebraska, Missouri, Kansas and South Dakota, four of those states have already received permission from the U.S. Food and Drug Administration (FDA) to blend corn in order to reduce the concentration of aflatoxin and requests from other states are pending. Those waivers are designed to reduce the aflatoxin concentration to less than 20 parts per billion.
The 20 parts per billion is the upper limit for food grade corn. For fluid milk, the upper limit for aflatoxin is .5 part per billion (ppb).
For some categories of livestock, several multiples of the food grade limit on aflatoxin are generally acceptable. Those limits go up to 100 ppb for breeding stock of cattle and swine and mature poultry, up to 200 ppb for finishing swine over 100 pounds, and up to 300 ppb for beef cattle being finished for market.
Corn growers who are putting their crop into storage without having it tested for aflatoxin are being advised to dry it quickly at temperatures between 120-140 degrees and not at 80-100 degrees because the latter temperatures allow more growth of the aspergillus mold which produces aflatoxin.
For winter storage, corn growers are being reminded that fungus growth that leads to aflatoxin thrives at temperatures of 75-79 degrees and 18-25 percent moisture in grain corn. The fungus is not active at temperatures below 60 degrees or in corn with 15 percent or lower moisture, but freezing does not kill the toxins already in the stored corn.
Other threats in corn include fusarium mold, which is most dangerous for horses and swine, and pencillium, which generally develops during storage. With corn silage, especially that which was dry when ensiled, poorly packed, or contaminated with soil, there is a possibility of the production of several types of mycotoxins or toxic acids.
According to Iowa State University grain quality specialists and agronomists, there appears to less fungal disease in the wake of this year's drought than there was in 1988. They attribute this to the biotech traits that have been built in most corn hybrids since then.
Questions about mycotoxins can be directed to the Mycotoxin Hotline at 1-866-322-3484.
Another information source is the Kentucky-based Alltech Company, which has developed a spectrometry test that can check 38 different mycotoxins in a quantitative manner and more than 50 others in a qualitative way in as little as 15 minutes.