Mycotoxins are natural contaminants of food products and feeds. It has become absolutely clear, since the discovery of aflatoxins, that under natural conditions it is not only peanuts but many other vegetable substrates are a favorable media for the growth of microscopic fungi and the development of aflatoxins. There is convincing proof about the possibility of transmitting aflatoxins to farm animals tissues provided there is a high aflatoxin content in feeds.