The federal Food and Drug Administration on Dec. 11 issued its final guidelines designed to eliminate the use of antibiotics to enhance growth in feed animals, largely cattle, pigs and chickens.

In addition, those antibiotics no longer will be available over the counter, meaning veterinarians will have to prescribe them for use in feed animals.

Antibiotics are widely used in feed animals to help them gain weight more quickly and use less feed in the process. That makes good sense from the producer’s point of view: The quicker an animal goes to slaughter and the less it eats getting there means the producer spends less on his crop.

But there’s a downside to the broad use of antibiotics on feed animals, and, in fact, such use has declined since the problem first was pointed out in the 1970s. Even at today’s subtherapeutic levels, however, they add to the problem of growing antibiotic resistance in microbes in humans. That, in turn, makes treating infection in humans more difficult and expensive than it otherwise would be.

Rather than ban the drugs’ use for weight gain, the FDA is asking some 25 drug manufacturers, including Eli Lilly & Co. and Zoetis, two of the largest, to remove “production” — weight gain — as an approved use. If they comply, as Lilly and Zoetis have said they will, using the drugs in that way becomes illegal. Manufacturers have three months to tell the agency what they will do.

The proposals, which apply only to drugs considered important for humans, have their critics who worry the guidelines are not strong enough. According to Reuters, David Krempa, an analyst for the investment research firm Morningstar, believes that the guidelines will not produce the desired result. He notes that similar guidelines were issued in April 2012 and compliance with them has been spotty.

The FDA disagrees, Michael Taylor, the agency’s top food safety official, said. He notes that if voluntary compliance is weak, the agency still can go back and make the guidelines mandatory.

We hope he’s right.

While getting critical antibiotics out of the food supply is only part of the solution to microbes’ increased drug resistance, it is a critical part.