Aflatoxin contamination of corn

Mycotoxins are produced by molds in several feedstuff, but most concerns of livestock producers revolve around aflatoxin contamination of corn. Aflatoxin is produced by the fungus Aspergillus flavus, which thrives during conditions of high humidity and high temperature at harvest time. Insect damage to the grain also increases the amount of fungal growth because it allows entry into the grain. Aflatoxin contamination appears to be more of a problem during drought stress. In addition, if corn is not properly dried down, aflatoxin levels can increase greatly during storage.

All classes of livestock can be affected by aflatoxins, but some are more sensitive than others. Poultry and swine are more sensitive than cattle and sheep. Younger animals of all species are more sensitive than mature animals. Effects of aflatoxins include feed refusal, decreased weight gains, decreased milk production, decreased resistance to infection, decreased reproductive performance, and even death at high levels of contamination. Lactating dairy animals are a special concern because low levels of aflatoxins in the feed can result in unacceptable levels passing into the milk. This can lead to a producer's milk being dumped.

The following guidelines for feeding levels of aflatoxins are considered safe under normal conditions. Animals under stress or disease situations may react to lower levels.

• Corn containing greater than 20 ppb should not be fed to young animals of any species.
• The total rations of lactating dairy cows should contain less than 20 ppb on a dry basis.
• The total ration of breeding swine, lactating beef cows, and weanling cattle should contain less than 100 ppb.
• The total ration of finishing swine, over 100 pounds, should contain less than 200 ppb.
• The total ration of dry beef cows and yearling cattle should contain less than 300 ppb.
• Rations for stressed feeder cattle should contain no more than 20 ppb of aflatoxin. Stressful conditions include weaning, shipping, extreme heat or cold, diseases, and parasites.

Producers should be concerned about aflatoxins but not panic. By being aware of the potential danger, steps can be taken to avoid problems. These steps include:

• Buying or harvesting high quality corn and drying it below 14 peracent moisture before storing.
• Screening corn to clean it of broken and damaged kernels can lower the level of aflatoxin contamination since levels are highest in damaged corn. However, this means that producers who are fond of using corn screenings should be especially concerned about aflatoxins.
• If there is reason to suspect a problem, get a good representative sample of the corn and have it checked for aflatoxins prior to feeding it. Using a blacklight test is of questionable value since it tends to give a lot of false positive readings. If it is determined that aflatoxins are present, then send a sample to the Mississippi State University Chemical Laboratory or a private lab to determine the actual concentration. Aflatoxin analyses are usually performed about 2 or 3 days after reaching the state laboratory at a cost of $30.00 per sample. Once a level of contamination is determined, you can work with a nutritionist to determine how much of this corn can safely be fed.

Aflatoxin is a real concern this year but it can be dealt with if producers are aware of the potential dangers and realize that the best treatment is preventing animals from consuming high levels. Please let us know if we can be of further assistance in dealing with aflatoxin questions. (Animal Dairy Sciences Department 662-325-3516)