There are published guidelines on all mycotoxins. Some of those are based on legal limits to trade grain as well.
From tests on corn grain this year, vomitoxin and zearelenone are the two primary mycotoxins showing up. But, there are many different types as described in the information below in the NebGuides..
Feedlot cattle are the most logical place to use feeds high in mycotoxins and level will dictate the amount used. Distillers grains could contain mycotoxins if the grain contains them. Because the starch is removed from the grain, which id 2/3 of the composition of the kernel, the mycotoxins are concentrated by two or three times in distillers. This may or may not be much of an issue, and ethanol plants will have to be diligent.
For feedlot that are using their home grown corn grain, if there appears to be a problem with the corn grain, consider sampling the grain and testing for mycotoxins. The Nebraska Department of Ag can help you locate a laboratory that can do the testing.
There are other resources that described corn ear rots and grain molds that also illustrates some of the more common ear rot diseases that are occurring in the 2009 corn crop. Please see the October 23, 2009 CropWatch article "Ear Rots and Grain Molds Are Common This Year".
The Beef Cattle Management Update (PDF 52KB) article from the University of Minnesota folks provides indepth information.
Finally, there is a very good article in the 2010 Feedstuffs Reference Issue (September 16, 2009) page 70-78 by Whitlow and Hagler, Jr. from North Carolina State.
Dr. Galen Erickson, Associate Professor of Animal Science
Animal Science, University of Nebraska–Lincoln, Lincoln, Nebraska