Increasingly many microbes that cause human disease are becoming resistant to antibiotics, in large part because the drugs are now more often used when they are not really needed. Much of the blame for this excessive use may fall on the meat industry, which frequently feeds antibiotics to livestock animals from birth to slaughter to promote growth. According to a new study from the Union for Concerned Scientists, meat producers feed some 25 million pounds of antibiotics to chickens, pigs and cows for non-therapeutic purposes each year. That figure represents about 70 percent of all antibiotics produced annually in the United States, and is considerably higher than some of the industry's own estimates. Stated another way, the amount of antibiotics fed to healthy animals is eight times greater than the amount given to sick people, which is 3 million pounds per year.

The report, Hogging It: Estimates of Antimicrobial Abuse in Livestock, states that industry feeds some 10 million pounds of antibiotics to healthy hogs each year; 11 million pounds to poultry; and 4 million pounds to cattle. Lacking government-backed data, the authors of the report instead devised a way to determine antibiotic use in livestock from information available in public documents, including herd sizes, approved drug lists and dosages. Based on what they found, they urge the pharmaceutical and livestock industries to supply more complete data to the public so that it will be easier for scientists to explore any connections between the drugs used in animals and the spread of resistance. They also recommend that government agencies get more involved. "The government should act now to collect the needed data," says Margaret Mellon, co-author of the report. "The price of complacency could set us back to an era where untreatable infectious diseases are regrettably commonplace."