The New York Times just published an article about antibiotic use in factory farming. From the article:
Dispensing antibiotics to healthy animals is routine on the large, concentrated farms [aka "factory farms"] that now dominate American agriculture. But the practice is increasingly condemned by medical experts who say it contributes to a growing scourge of modern medicine: the emergence of antibiotic-resistant bacteria, including dangerous E. coli strains that account for millions of bladder infections each year, as well as resistant types of salmonella and other microbes. [...]
Scores of scientific groups, including the American Medical Association and the Infectious Diseases Society of America, are calling for even stronger action that would bar most uses of key antibiotics in healthy animals [...]
“Is producing the cheapest food in the world our only goal?” asked Dr. Gail R. Hansen, a veterinarian and senior officer of the Pew Charitable Trusts, which has campaigned for new limits on farm antibiotics.