Health hazards from animal feedstuffs

A widespread practice in animal husbandry in recent years has been to add substances to animal feeds in order to promote their growth or protect them against diseases which could kill them or stunt their growth. These substances include a wide variety of antibiotics and other chemotherapeutic agents (such as antiprotozoal and antibacterial compounds), vitamins and other concentrated and synthetic food substances. The drugs are presumed to act mainly as suppressors of disease agents, although they may also exert as yet ill-defined non-specific effects that promote animal growth. Undesirable effects of food additives include the emergence of antibiotic-resistant strains of micro-organisms that, when transferred to man, may cause considerable medical and public health problems. Allergic reactions and toxic effects in man may also occur. Unmetabolised drugs are excreted and may enter natural ecological cycles, contaminating wild animals.