Citing a potential threat to public health, the Food and Drug Administration is taking steps toward phasing out the use of some antibiotics in animals processed for meat.

Many cattle, hog and poultry producers give their animals antibiotics regularly to ensure they are healthy and to make the animals grow faster. Now, the agency has announced that it will ask pharmaceutical companies to voluntarily stop labeling drugs important for treating human infection as acceptable for growth promotion in animals.

If the companies sign on — and one major company has already said it will — using those antibiotics to promote growth in animals would be illegal. Prescriptions would be required to use the drugs for animal illnesses.

The FDA has been debating how to address the issue of antibiotics in meat for several years as consumers have become more aware of the issue and are clamoring for antibiotic-free meat.

The FDA move is designed to limit antibiotic-resistant diseases in humans. Repeated exposure to antibiotics can lead germs to become resistant to the drug so that it is no longer effective in treating a particular illness.

Antibiotic resistance is a growing public health problem. In September, the Centers for Disease Control and Prevention released sobering estimates that more than 23,000 people a year die from drug-resistant infections.

The biggest risk is from germs spread in hospitals, and it’s not clear how much of the problem is related to the use of drugs in meat. Still, the FDA says this is one step toward decreasing resistance.

“We need to be selective about the drugs we use in animals and when we use them,” said William Flynn of the FDA’s Center for Veterinary Medicine. “Antimicrobial resistance may not be completely preventable, but we need to do what we can to slow it down.”

The new guidance will give the companies three years to comply.

Michael Taylor, the FDA’s deputy commissioner of foods, said he believes asking industry to make the changes is the fastest way to help phase the drugs out. If the FDA made the process mandatory, he said, the agency would have had to move forward with a complex regulatory process that could take years.

“We have high confidence based on dialogue with industry that this initiative will succeed,” Taylor said.

Drug company Zoetis, a leading manufacturer of animal antibiotics, has already said they will comply.

“This reflects our continued commitment to antibiotic stewardship and represents the many ways that Zoetis promotes the responsible use of antimicrobial drugs in animals,” the company’s statement said.

Animal agriculture groups will not have much of a choice in the matter if drug companies sign on and make the drugs’ use illegal. But many antibiotics will still be available for those producers to use, just not those that the FDA has classified as most important for treating human infections. Some of the antibiotics that could not be used in animals are penicillins and tetracyclines, the FDA said.

Some advocates pushing to rid the animal food supply of antibiotics said the FDA did not go far enough. Democratic Rep. Louise Slaughter of New York, a microbiologist, said the FDA should have made the action mandatory. The guidance “falls woefully short of what is needed to address a public health crisis,” she said.

Others hailed the agency move as progress.

“We commend FDA for taking the first steps since 1977 to broadly reduce antibiotic overuse in livestock,” said Laura Rogers of the Pew Charitable Trusts’ human health and industrial farming campaign. “There is more work to do, but this is a promising start, especially after decades of inaction.”