By the 1970s, public health officials had become worried that overuse was leading to the development of infections resistant to treatment in humans. In 1977, the F.D.A. announced that it would begin banning some agricultural uses. But the House and Senate appropriations committees — dominated by agricultural interests — passed resolutions against the ban, and the agency retreated. In the years since, the issue of antibiotic overuse in animals and drug resistance has become one of the leading public health concerns worldwide. Those concerns have over recent years even convinced some in the agricultural community that action was needed.

The new rules generated mixed reactions from both public health advocates and agricultural trade associations. Laura Rogers of the Pew Campaign on Human Health and Industrial Farming called the new rules “the most sweeping action the agency has undertaken in this area,” while Caroline Smith DeWaal of the Center for Science in the Public Interest criticized them as “tragically flawed” because they relied too much on voluntary industry efforts.

The Animal Health Institute, an association of animal drug makers, welcomed the new rules. But R. C. Hunt, president of the National Pork Producers Council, said that small farmers and ranchers would have a hard time following the new rules, which “could eliminate antibiotics uses that are extremely important to the health of animals.”

Initially, the F.D.A. is asking drug makers to voluntarily change their labels to require a prescription; federal officials said that drug makers had largely agreed to the change. If some fail to impose the restrictions, the agency will consider a more forceful ban, Mr. Taylor said.

The reason for the reliance on voluntary efforts is that the F.D.A.’s process for revoking approved drug uses is lengthy and cumbersome, officials said. The last time the F.D.A. banned an agricultural use of a medically important antibiotic against the wishes of its maker, legal appeals took five years. In this case, hundreds of drugs are involved, each with myriad approved uses in various animals.

“You and I and our children would be long dead before F.D.A. could restrict all of these uses on its own,” Ms. Rogers said.

Last month, Judge Theodore H. Katz of the Southern District of New York ordered the F.D.A. to begin the process to ban indiscriminate agricultural uses of penicillin and tetracycline because of dangers to human health. The agency hopes that the rules it announced Wednesday achieve the same result.