Aflatoxin is a toxic and carcinogenic substance produced by certain strains of the moulds Aspergillus flavus and A. parasiticus. When ruminants consume grain containing aflatoxin, they create a metabolite which is found in their milk, aflatoxin M1. Ingesting excessive amounts of the toxin can cause chronic health and performance problems or death in animals. Aflatoxin has been shown to cause liver damage or cancer, decreased milk and egg production, immune system suppression and interference with reproductive efficiency.