Animal feeds are routinely subject to contamination from diverse sources, including environmental pollution, activities of microbes, and veterinary drug residues. Contamination of feed with chemical substances such as coccidiostats or antibiotics can occur at the stage of production, transport and storage, and their presence may have a negative impact on the health of animals consuming feed contaminated with certain chemicals. This study presents the legal requirements for the production of feed, the presence of antimicrobial substances in feed, and the problem of contamination of feed with antibacterial substances as well as the possible transfer of these compounds to the animal tissues and the natural environment.