All feeds have the potential to produce chemicals which are toxic to dairy cattle.
The four most common aflatoxins are B1, B2, G1, and G2. Contaminated grains and grain byproducts are the most common sources of aflatoxin. Corn silage may also be a source because the ensiling process does not destroy the toxins already present in silage. Aflatoxins are metabolized in the liver and excreted in the bile. When significant quantities of B1 are consumed, the metabolite M1 appears in milk within 12 hours.