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Aflatoxin Could Be A Problem on Midwestern Corn This Year
Agronomy | August 18, 2005

By Ed Zdrojewski, Grain Journal editor

In most years, aflatoxin is a common problem on corn grown in the hottest and dryest regions on the United States.

Grain elevator managers in those regions are well aware of the problem and are equipped to test incoming loads routinely.

In other parts of the country, aflatoxin contamination is rarely a problem. However, this year, with “Texas”-like weather conditions extending into the Corn Belt, with extreme drought and high temperatures through the growing season, elevator managers across the Corn Belt may need to consider a strategy for dealing with aflatoxin.

Here, in an easy-to-use Q&A format, is some basic information about aflatoxin and how to deal with it.

For more information, contact the U.S. Department of Agriculture’s Federal Grain Inspection Service (FGIS) Technical Services Division at 816-891-0401 or the Office of the Texas State Chemist at 979-845-1121. See below for web links.

What is aflatoxin?

Aflatoxin is considered a mycotoxin, which is a compound produced by a mold. More specifically, aflatoxin is a byproduct produced by the Aspergillus flavus or Aspergillus paraciticus mold.

Four types of aflatoxin are found on grain, B1, B2, G1, and G2. They are so designated because after extraction from grain, B1 and B2 will glow blue under a black light, and G1 and G2 glow green under a black light.

B1 is the most common and also the most potent type of aflatoxin.

Why is aflatoxin a problem on corn?

Aflatoxin is the most potent naturally-occurring carcinogen known to man. At high levels, it can cause liver cancer in humans and other animals.

It also has been suspected for causing hemorrhaging of the intestinal tract and kidneys and can suppress the immune system and suppress appetite.

Different animals are affected at different levels of consumption.

When is aflatoxin most likely to become a problem on corn?

Aspergillus mold spores are always present in the environment and are waiting for the correct conditions to grow and produce aflatoxin.

Corn growing in the field can produce aflatoxin when nighttime temperatures are around 75 degrees F or higher and daytime temperatures are over 90 degrees consistently.

However, it typically also takes drought conditions for aflatoxin production, when insects in the field carry the spores with them beneath the husks. The insects then chew the kernels, resulting in an intrance point for the mold spores to start growing.

Aflatoxin also can be produced by the mold growing in storage, with corn at a minimum 14% moisture and 68 degrees temperature. If stored corn is a mixture of high and low moisture content, the mold can grow and produce aflatoxin on the wet kernels.

In the southeastern United States, corn harvested late in the day and left overnight in the truck has been known to increase in aflatoxin levels significantly.

How much aflatoxin must be present in corn or corn products before there is a problem?

The U.S. Food and Drug Administration (FDA) has set a series of action limits for aflatoxin, depending on the species to which the grain will be fed. The limits are as follows:

  • 20 parts per billion (ppb) for humans, immature animals (including poultry), all dairy animals, and when the end use of the grain is not known.
  • 100 ppb for breeding beef cattle, swine, and mature poultry.
  • 200 ppb for finishing swine (100 lbs. and up).
  • 300 ppb for feeder cattle.

Which elevators should be prepared for aflatoxin-contaminated grain?

Elevator managers in the southwestern states routinely experience aflatoxin contamination most years and, for the most part, are prepared to deal with it.

This year, with extreme drought and high temperatures affecting a wide swath of the Midwest, especially across most of Illinois, eastern Iowa, and northeastern Missouri, elevators in or near the drought area should have an aflatoxin strategy in place.

Since hot weather has been prevalent everywhere in the Midwest this year, elevator managers elsewhere should seriously consider having a plan in place, as well.

The strategy should include plans for testing incoming loads, rejecting loads with high levels of contamination, and blending to reduce contamination below FDA action levels, depending on the intended use of the corn.

How do you tell if an incoming load of corn is contaminated and the level of the contamination?

Aflatoxin itself is not directly visible on the grain, so some sort of testing is necessary.

In the past, elevators commonly exposed grain samples to black light to see if they glowed blue or green, which could indicate the presence of aflatoxin.

However, this is an indirect measurement of aflatoxin that can miss some contaminated samples and does not indicate the level of contamination. The FGIS Official Inspection System no longer accepts black light testing as definitive.

The accepted standard for testing incoming loads at the grain elevator are quick tests based on the ELISA assay method. Test kits that are approved for use in the Official Inspection System are available from a number of manufacturers:

When using a quick test, care must be taken to obtain a representative sample from the incoming load, and a sufficient sample size is needed. FGIS specifies a 10-lb. sample, while the Texas Office of the State Chemist typically uses a 20-lb. sample.

What should be done when aflatoxin is found?

That depends on the level of infestation and the intended end use of the product.

In Texas, where aflatoxin is found routinely, most elevators will automatically reject any load that exceeds 300 ppb. Some states prohibit any food or feed use for corn that exceeds 500 ppb.

Aflatoxin contamination may not be a concern at any level for certain industrial uses of corn. However, it may be a problem for some industrial uses, such as ethanol production, since distillers dried grains from the production process typically are sold for feed use.

Elevators should be prepared to segregate corn over a certain level of contamination, again depending on the intended end use.

FDA generally does not permit corn containing aflatoxin to be blended with uncontaminated corn to reduce the aflatoxin content of the resulting mixture to levels acceptable for use in human food.

However, according to a Feed Quality Assurance Program manual published by the National Grain and Feed Association, FDA on occasion has relaxed its “no-blending” policy in response to widespread outbreaks of aflatoxin, as occurred in 1988, or in response to state-specific requests to address local outbreaks, as occurred in Missouri in 1993.

Also, FDA technically does not consider mixing of corn containing a level of aflatoxin up to the action level that is “acceptable” for a given species to be a violation of its no-blending policy.

For example, since corn containing aflatoxin of up to 300 ppb that is intended to be fed to mature beef cattle is in compliance with FDA’s action level for that species, technically any corn containing less than 300 ppb may be mixed and fed to that particular species, without violating FDA’s no-blending policy.

By contrast, mixing corn containing up to 200 ppb with uncontaminated corn (less than 20 ppb) so as to reduce the level of aflatoxin in the resulting measure to 50 ppb, so it could be fed to laying hens, constitutes a violation of the no-blending policy since a 100-ppb action level applies to mature poultry.

3 Responses

  1. January 26th, 2006 | Andy Sicard Replied:

    Charm Sciences, Inc. also offers test kits that are approved for aflatoxin testing/screening in the Official Inspection System.

    For more information visit the Charm Sciences website at: http://www.charm.com
    or http://www.charm.com/pdf/rosa_aflatoxin_tests.pdf

    Andy Sicard
    Marketing Communications Manager
    Charm Sciences, Inc.

  2. September 13th, 2006 | Frank Visco Replied:

    Hello:
    Are there any figures available for corn on the yearly infection rates for aflatoxin producing fungi in different regions in the U.S.?
    Thank you,
    Frank Visco
    Professor of Biology
    Orange Coast College
    Costa, Mesa, CA

  3. September 14th, 2006 | Clint Hawks Replied:

    Frank,

    Here’s what google came up with >>

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