Feedstuff is a common standard for each kind of food for animals, which are in the charge of man and serve as food. Feed for livestock is of special interest. The quality of feed is responsible for the health of animals and indirectly for the quality of human nutrition. Agriculturally used plants, such as numerous grains, oil seeds and nuts, root crops, and to a smaller extent, many forage crops are susceptible to mycotoxin contamination. Fungal and in the end mycotoxin contaminated feed may be involved in modern livestock production practice (confined rearing on high-density diets) because plant feedstuff especially from multiple sources may be used for feeding. The mixing of mycotoxin contaminated pecan, walnut, or other nut meats into feedstuff is one example. The nuts are pressed to recover the oil while most of the toxin is concentrated in the residual meats. The press cake usually is diverted into animal feed channels. The amount of these (protein supplement) ingredients, while small, could cause problems in the health of animal and human. Available data suggest that the mold and mycotoxin problem is largely one of the worldwide feed management. Especially individual farm silos and feed troughs are major sites of toxin production in mold-contaminated feeds. Guidelines for the investigation and amelioration of feedstuff quality in different countries have been prepared. Mycotoxin contamination of feeds occurs as a result of crop invasion by field fungi.