Overuse in Farm Animals

Although no definitive data are available, the estimates that 70% of antibiotics in the U.S. are fed to pigs, poultry and cattle – not to treat illness, but rather to promote slightly faster growth and to compensate for crowded, stressful, and unsanitary conditions. Recent studies, including one by the World Health Organization, show that ending the routine feeding of antibiotics to livestock and poultry can dramatically reduce the levels of resistant bacteria present in those animals. 

Why Use Antibiotics In Feed? 
Antibiotics have been put into animal feed since 1946, when experiments showed low levels of antibiotics could help food animals grow faster and convert feed into weight more efficiently. Antibiotics are used in 90% of starter feeds, 75% of grower feeds and more than half of finishing feeds for pigs in the U.S. Despite their widespread use, no one knows exactly how antibiotics work to promote growth in animals. 
Use of feed laced with antibiotics is both routine and common in America's version of industrial animal agriculture. Large confined animal feeding operations (CAFOs), which often raise pigs, poultry or cattle by the tens of thousands under crowded conditions, have replaced small-scale farms as the chief producers of the nation's beef, pork and poultry. They depend on antibiotics in animal feed not only to promote growth but also to compensate for crowded and often less-than-hygienic conditions, which stress the animals and make them more prone to infection. Unfortunately, low-level use of antibiotics for extended periods of time is one of the best ways to speed the development of antibiotic-resistant bacteria.

Human Antibiotics Commonly Used 
The same mechanisms by which bacteria in humans develop resistance also work in animals that are fed antibiotics. The genes that confer antibiotic resistance to bacteria can travel from food animals to humans via several routes, including on contaminated food and through contamination of the environment

Many of the antibiotics routinely given to healthy livestock and poultry to promote growth are identical, or nearly so, to drugs that health providers rely on to treat sick humans. These include penicillin, tetracyclines, erythromycins and bacitracin, among others. For example, the Union of Concerned Scientists estimates that nearly 5 million pounds of two tetracycline antibiotics are fed to swine each year in the U.S. The volume of these two medicines fed to pigs alone, according to UCS estimates, is sixty percent greater than the volume of all antibiotics given to sick humans. 

Alternatives to Antibiotics Available 
Europe is moving in the direction of a total ban on routine use of antibiotics in animal feeds. Sweden and Denmark have already completed a phaseout, while other European Union countries have ended such uses of most antibiotics and are scheduled to end use of the rest by 2006. These nations have led the development of large-scale livestock management techniques that use better hygiene rather than antibiotics to raise healthy animals, with no interruption in the meat supply. A growing roster of U.S. producers also avoids routine use of antibiotics.