Monitoring of residues of hormonally active and prohibited substances in food materials of animal origin

Hormonally active substances (e.g. anabolic steroids) and residues of pharmaceutical drugs prohibited from use in food-producing animals (e.g. chloramphenicol or metronidazole) are monitored in biological matrices (tissues, urine, blood plasma) as part of regular official tests for the presence of banned substances in animals intended for food production. Any such residua found in farm animals are considered a proof of illegal administration of a banned substance, and in such cases, an official investigation of the livestock’s owner is conducted, a fine is imposed and the contaminated food materials are prevented from entering the food chain and are destroyed at the owner’s expense. The finding of residues of substances that are banned for use in food-producing animals but could, at the same time, be endogenous in animals, poses a problem in practice. This article describes several procedures that could be used to distinguish between illegal administration of a banned substance and endogenous residues in farm animals.