Antimicrobial substances — originally microbial products, now also fully synthetic — that kill or inhibit bacteria. In food-animal production they treat and prevent infections, but every use is bounded by maximum residue limits, mandatory withdrawal periods and tightening stewardship rules aimed at slowing antimicrobial resistance. Surveillance programmes screen meat, milk, eggs and honey for penicillins, tetracyclines, sulphonamides and other classes. The central tension is real: sick animals need treatment, yet overuse breeds resistant bacteria that threaten human medicine. Growth-promotion uses are now banned or phased out in most major markets.