F.D.A. to Phase Out Use of Some Antibiotics in Animals Raised for Meat WASHINGTON - The Food and Drug Administration said Wednesday that it is taking steps to phase out the use of some important antibiotics in animals raised for meat, a step that public health advocates said would help preserve the effectiveness of drugs critical to human health after decades of inaction by the agency. Antibiotics, one of the wonder drugs of the 20th century, were initially used indiscriminately in people and animals, experts say. Farmers discovered that antibiotics helped animals grow much more rapidly and added the drugs to feed and water given to healthy animals. Broad use has led to antibiotic resistance, and some of these critical drugs no longer work in treating infections, experts say. Under its new plan, the agency has changed the rules so that food animal producers will no longer be able to use antibiotics to make animals grow faster. And if producers need to give the drugs to a sick animal, they will have to get a prescription from a veterinarian. The changes were originally proposed in 2012. The agency will ask the drugs" manufacturers to change labels to rule out using the medicines to make animals grow. The changes are voluntary for drug companies, but F.D.A. officials said they believed the companies would comply. Companies will have three months to tell the agency whether they will change the labels, and three years to carry out the new rules. "Based on our outreach, we have every reason to believe that animal pharmaceutical companies will support us in this effort," said Michael Taylor, the F.D.A.'s deputy commissioner for foods and veterinary medicine. One drug producer, Zoetis, said it approved of the changes. "We believe that veterinarians should be involved in decisions regarding antibiotic use in food animals for the health of the animal and for the safety of the food supply," the company said in a statement. Just how broadly farmers use antibiotics simply to promote animal growth is unknown. About 80 percent of antibiotics used on farms are given through feed, and an additional 17 percent are given in water. Just 3 percent are given by injection. Public health advocates applauded the move. "Restricting the use of antibiotics for growth promotion and increasing veterinary oversight is a promising start," said Laura Rogers, director of the Pew Charitable Trusts" human health and industrial farming campaign. We're particularly encouraged that major drug makers are indicating they will comply and that the F.D.A. acknowledges there is still more work to do.