FRI BRIEFINGS Alternatives to Antibiotic Use for Growth Promotion in Animal Husbandry

Since the discovery and development of the first antibiotics prior to the Second World War, these drugs have played an important role in curing disease in humans and animals. In 1946 experiments showed that low, subtherapeutic levels of antibiotics could increase feed efficiency and growth in food animals, and the addition of various antibiotics to feed for livestock was initiated. Because prevention of disease transmission and enhancement of growth and feed efficiency are critical in modern animal husbandry, there has been widespread incorporation of antibiotics into animal feeds in many countries (74, 144). Swine feeds in the U.S. often contain antibiotics for purposes of disease prevention and growth promotion. According to data from USDA and Animal Health Institute, antibiotics are currently used in 90% of starter, 75% of grower and more than 50% of finisher feeds for pigs (34, 37, 38, 55, 173). Antibiotics have also been widely used in animal feed in many other countries although a number of individual countries and the European Union have recently restricted the subtherapeutic use of some antibiotics (3, 138, 147, 156, 166). Precise figures on the relative amounts of antibiotics used in humans and in animal agriculture are impossible to obtain. Various estimates have been calculated by the Institute of Medicine (34, 74, 174), the Animal Health Institute, a trade organization (172), and the Union of Concerned Scientists (174). Human use of antibiotics has been estimated at 1.36–14.64 million kg/yr while estimated antibiotic use in animal agriculture is 7.36–11.18 million kg/yr. Although estimates from different sources are not directly comparable, it is clear that there is significant use of antimicrobial agents both in human medicine and in agriculture. Currently, the potential for agricultural antibiotics to contribute to the development of antibiotic-resistant bacteria of human concern is the subject of intense debate and research (3, 74, 163, 166).