The National Chicken Council, an industry group, said in a statement that the sale of antibiotics did not necessarily correlate with antibiotic resistance trends. It said that most antibiotics used in chicken production were not used in human medicine.

The report did not differentiate by species; it included all animals raised for meat.

Antibiotics were the wonder drugs of the 20th century, and their initial use in humans and animals was indiscriminate, experts say. Farmers learned that antibiotics helped animals grow rapidly, and they began to add the drugs to feed and water, with no prescriptions or sign of sickness in the animals. But it is now known that broad use leads to antibiotic resistance, which means that critical antibiotics are no longer as effective in treating infections in people.

The United States also uses far more antibiotics in livestock than many other nations, according to Pew. Animals raised for food in America are given about six times as much antibiotics as are animals in Norway and Denmark, for example.

The most sweeping federal policy aimed at curbing antibiotics use in animals was introduced last year, when the F.D.A. asked companies that make the drugs to change the labels. Those changes meant that food animal producers would no longer be able to use antibiotics to make the animals grow faster. And if food animal producers wanted to give the drugs to a sick animal, they would need to get a prescription from a veterinarian.

But consumer health advocates said at the time that it was unclear that the changes would have much effect. The rules left open a large loophole: Producers could simply argue that they were using the drugs to keep their animals from getting sick, not to make them grow faster.