ABSTRACT
The use of drugs as additives in animal feeds has been approved since the early 1950s. Veterinary drugs are intended to maintain or improve the health of animals used for human food purposes. The food-producing animals in which veterinary drugs are approved for use comprise cattle, pigs, sheep, goats, poultry, and fish. The challenges of global population growth have led to increased efforts to find resources to enhance animal food production to its maximum. The developments in animal husbandry during the past 50 years have resulted in a proliferation of intensive production units, especially for pigs and poultry, where these animals are kept in limited space. Earlier such intensive units were prone to outbreaks of disease that could decimate them. It was soon found useful routinely to feed low levels of antibiotics prophylactically to animals to prevent the initial outbreak. The prophylactic treatment of animals with other drugs at low concentrations often improves the growth rates of these animals quite significantly, and hence, the practice grew, as did the use of hormones that are natural growth promoters.
