While experts initially expressed concern that fungi-produced chemical compounds known as aflatoxins might damage U.S. corn yields thanks to the drought, results appear mixed.
In September, experts with the University of Illinois reported that some milk had been turned away because of unacceptable aflatoxin levels. Also that month, experts at Purdue University advised farmers to be on the lookout for the mold-like substance, whose presence can vary widely depending on environmental factors and planting time.
But the news hasn’t been all bad. Experts at Michigan State University reported this month via CattleNetwork.com that aflatoxin has been less prevalent than expected.
John Leslie is a distinguished professor who heads the plant pathology department at Kansas State University. In an email interview this week, he explained why aflatoxins can be cause for concern; described its relationship with drought; and shared his thoughts on the USDA’s decision to allow blending of corn containing aflatoxins.
What is aflatoxin, and why is it a concern for corn farmers?
Aflatoxins are a family of structurally related chemical compounds synthesized by a number of species of fungi in the genus Aspergillus, with Aspergillus flavus the fungus usually of greatest interest and aflatoxin B1 usually the most important aflatoxin.
Aflatoxins are toxic to humans and many other animals at sufficiently high levels, although for humans the more common fear is their carcinogenic capabilities and the increase in liver cancer as a result of exposure to them. Long-term chronic exposure to sub-clinical levels of aflatoxins can result in partial suppression of the immune system, rendering those so exposed generally less resistant to other microorganisms to which the individual might be exposed.
Human deaths due to aflatoxins in the U.S. and other developed countries are rare because our food regulatory system usually identifies contaminated materials and restricts their entry into the commercial food and feed chains. There have been outbreaks of aflatoxin poisoning in Africa, most recently Kenya, in which several hundred people have died due to aflatoxin poisoning from eating corn containing too much aflatoxins.
There are currently major multi-national efforts to reduce the level of aflatoxin in both corn and peanuts in Africa to reduce the health problems these compounds can cause there. The most recent aflatoxin problem in the U.S. occurred a few years ago when contaminated dog food killed a number of pets.
Earlier this year, the USDA authorized states such as Iowa, Illinois and Nebraska to blend aflatoxin-affected corn with unaffected corn. Is this normal? How does this decision benefit farmers, and what should consumers know about these blends?
Maximum aflatoxin levels allowed in corn are set in the U.S., with the exact level determined by the end use for which the corn is intended. Aflatoxin can be carried through the milk of an animal that consumes corn contaminated with the toxin. Thus grain intended for dairy cattle feed, for example, is allowed to have much less aflatoxin contamination than is grain intended for beef cattle.
Blending allows the mixing of grain with a lower level of aflatoxin with grain that has higher levels of aflatoxin, i.e. grain exceeding the regulatory limit, so that the final mixture is below the regulatory threshold. USDA usually does not allow the grain to be blended and rejects the contaminated grain to keep it out of the food system.
The blends being allowed this year will still be safe and will meet all of the food regulatory standards. The blends probably will have levels of aflatoxin that are closer to the limits than might be found in other years.