The issue with distillers grains is that you take the starch out of the kernel, and are left with the part of the kernel where the aflatoxin is located. Thus, you have concentrated the aflatoxin into the distillers grains, instead of having it in the whole grain. It can kill all types of cattle, but, like nitrates, takes a higher concentration to kill than to cause abortions. Aflatoxin is another product that is naturally occuring and always present in the corn plant, but any injury/stress make it worse. Hail/drought could make it bad; earworms, if bad enough, can make it really high as it opens the plant up to infection right at the kernel.