DON is another mycotoxin of concern to some importers of corn grain. It is produced by certain species of Fusarium, the most important of which is Fusarium graminearum (Gibberellazeae) which also causes Gibberella ear rot (or red ear rot). Gibberellazeae can develop when cool or moderate and wet weather occurs at flowering. The fungus grows down the silks into the ear, and in addition to producing DON, it produces conspicuous red discoloration of kernels on the ear. The fungus can also continue to grow and rot ears when corn is left standing in the field. Mycotoxin contamination of corn caused by Gibberellazeae is often associated with excessive postponement of harvest and/or storage of high-moisture corn.
DON is mostly a concern with monogastric animals, where it may cause irritation of the mouth and throat. As a result, the animals may eventually refuse to eat the DON-contaminated corn and may have low weight gain, diarrhea, lethargy, and intestinal hemorrhaging. It may cause suppression of the immune system resulting in susceptibility to a number of infectious diseases.
The FDA has issued advisory levels for DON. For products containing corn, the advisory levels are:
- 5 ppm in grains and grain co-products for swine, not to exceed 20% of their diet;
- 10 ppm in grains and grain co-products for chickens and cattle, not to exceed 50% of their diet; and
- 5 ppm in grains and grain co-products for all other animals, not to exceed 40% of their diet.
FGIS is not required to test for DON on corn bound for export markets, but will perform either a qualitative or quantitative test for DON at the buyer’s request.