The C.D.C. report said that “much of antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe.” Then in December, the Food and Drug Administration announced a plan to curtail the use of antibiotics in animals.

Meat producers use antibiotics to prevent sickness in animals that are raised in close quarters in industrial farming operations. Chickens are treated, for example, with a small dose of gentamicin while still in ovo in an effort to prevent infection through a tiny hole made when the egg is administered a drug that prevents Marek’s disease and infectious bursal disease, highly infectious viral diseases that can wipe out flocks.

Antibiotics also are incorporated into feed commonly used by large producers to help animals grow faster and use feed more efficiently.

But producers are aware of the consumer demand for antibiotic-free meat. Bell & Evans, a smaller producer, has worked with its feed supplier to incorporate oregano into the kibble it feeds its chickens to act as a replacement for antibiotics, and Tyson last year started a line of chicken marketed under the label NatureRaised Farm, which is raised cage-free on a vegetarian diet without antibiotics.

Chick-fil-A already uses chicken breasts free from fillers, additives and steroids.

Rob Dugas, vice president for supply chain management at Chick-fil-A, said the shift would take time because it required changes by producers from the hatchery to the processing plant. “For instance, any flock treated with antibiotics today is aggregated into the larger production facility,” Mr. Dugas said. “For us, birds will have to be segregated all the way down to the egg production.”

Chick-fil-A executives said they could not say yet whether the changes would result in a price increase for consumers. Typically, antibiotic-free chicken is more expensive than traditionally processed poultry.

“We do know that it has a potential cost ramification, both to us and to our customers,” Mr. Tassopoulos said. “We are going to do everything we can to minimize the impact on the price of our products, and the growing interest in antibiotic-free meat may help with that by increasing supplies.”