But the Food and Drug Administration has tried without success for more than three decades to ban such uses. In the past, Congress has stepped in at the urging of agricultural interests and stopped the agency from acting.
In the battle between public health and agriculture, the guys with the cowboy hats generally win.
The F.D.A. released a policy document stating that agricultural uses of antibiotics should be limited to assuring animal health, and that veterinarians should be involved in the drugs’ uses.
While doing nothing to change the present oversight of antibiotics, the document is the first signal in years that the agency intends to rejoin the battle to crack down on agricultural uses of antibiotics that many infectious disease experts oppose.
Dr. Joshua M. Sharfstein, the agency’s principal deputy commissioner, refused at a news conference to give details about when the agency would take more concrete steps.
“We believe this is a public health issue of some urgency,” Dr. Sharfstein said. “We’re looking to see some progress soon.”
About 100,000 people die every year from hospital-acquired infections caused by bacteria that, because of overuse of antibiotics, have developed resistance to the usual remedies and cannot be killed with them. Many others die from superbugs contracted outside hospitals.
How many deaths can be attributed to agricultural uses of antibiotics?
“I don’t think anyone knows that number,” said Dr. James Johnson, a professor of medicine at the University of Minnesota, “but I think it’s substantial.”
Antibiotics are used in agriculture for three reasons: to promote animal growth, prevent illness and treat sickness. How antibiotics in feed and water help to fatten animals is not entirely clear.
The industrialization of animal husbandry has increased processors’ dependence on antibiotics because factory farm animals tend to be sicker and feed-lot diets can encourage bacterial infections.
The Union of Concerned Scientists estimated in 2001 that 84 percent of all antibiotics were used in agriculture and that 70 percent were used simply to promote animal growth, not to treat or prevent illness. The Animal Health Institute, a trade association, estimated that 13 percent of agricultural antibiotics were used to promote growth.
Dave Warner, a spokesman for the National Pork Producers Council, said most agricultural antibiotics were given to healthy animals not to promote growth but to prevent illness.
The distinction is important because F.D.A. officials said they were mostly concerned with the use of antibiotics to promote growth — not to prevent or treat illnesses. If the agency some day bans growth promotion as a use, there is a chance producers would simply relabel such uses as preventative.
Mr. Warner said his organization opposed the F.D.A.’s guidance. “We think this guidance could lead to the elimination or costly review of previously approved animal health products,” he said.
The Animal Health Institute said in a statement that it welcomed the guidance and had “long supported efforts to promote judicious use of antibiotics.”
Representative Louise M. Slaughter, Democrat of New York and chairwoman of the House Rules Committee, said the F.D.A. had “not gone far enough or moved fast enough.” Ms. Slaughter has proposed legislation banning nontherapeutic uses of some classes of antibiotics.
By GARDINER HARRIS Published: June 28, 2010