Antibiotics are regularly used in animal feed to fatten-up animals quickly, lowering producer's costs and increasing profits. But, according to this article in the Des Moines Register, "[d]octors and public health experts have long worried that there's a human price to using drugs this way": that the prevalence of antibiotics in animals, which ends up in food ingested by humans, is creating antibiotic-resistant bacteria that threaten human health. So, the Food and Drug Administration has issued a draft Guidance, entitled "The Judicious Use of Medically Important Antimicrobial Drugs in Food-Producing Animals," which proposes to "limit medically important antimicrobial drugs to uses in food-producing animals that are considered necessary for assuring animal health." As the Des Moines Register article explains, an earlier ban in Denmark seems to have had the desired effect:
Denmark . . . banned the growth-promotion use of antibiotics in the mid-1990s, cutting use of the drugs by 40 percent. More important, there's evidence that the ban reduced the amount of dangerous drug-resistant bacteria to which Danish consumers were being exposed. One type of bacteria found in hogs, campylobacter, is far less likely now to withstand a group of drugs known as macrolides than it was before the ban. Less than 20 percent of the bacteria was drug-resistant in 2006.
FDA's Principal Deputy Commissioner Josh Sharstein explained the FDA's view in his July 14, 2010 testimony to the Subcommittee on Health of the House Committee on Energy and Commerce.