The best estimate currently available is that nearly 25 million pounds of antibiotics are given to food animals for nontherapeutic purposes, such as growth promotion and disease prevention. When used nontherapeutically, antibiotics are given at low levels, usually over long periods of time. Animal factories rely on antibiotics to promote growth. USDA Antibiotics have long been fed to animals in the belief that they improve feeding efficiency and therefore increase farmers profits by enabling animals to reach slaughter weight on less feed. Although there is scientific support for the growth-promoting effects of antibiotics, it is difficult to separate the drug s effects from other factors that increase feed efficiency like reduced levels of stress and disease.
Animal factories rely heavily on growth-promoting antibiotics.
The intensely crowded and sometimes unsanitary conditions of modern industrial livestock production result in stressed animals. Today almost all of the over eight billion cattle, poultry, and swine raised for human consumption in the United States each year receive some type of antibiotic during their lifetime to promote growth. But this reliance on low-level use of antibiotics need not be a requirement for modern animal agriculture. 1 Antibiotics are a class of substances that kill or inhibit the growth of bacteria. Examples are penicillin and tetracycline.