The company said it does not use antibiotics for growth promotion in its chicken production, and has not since 2007.

The company does use an animal-only antibiotic to control an intestinal parasite, and will use antibiotics to treat and control illness in sick flocks.

"By no longer using any antibiotics in our hatcheries or any human antibiotics in feed, we’ve reached the point where 95 percent of our chickens never receive any human antibiotics, and the remainder receive them only for a few days when prescribed by a veterinarian," said Dr Bruce Stewart-Brown, Senior Vice President of Food Safety, Quality and Live Operations for Perdue Foods.

Eliminating use in the hatchery has taken five years to fully implement, and is the latest stage of a 12-year evolution in the company’s approach to antibiotic use. No antibiotics in the hatchery exceeds the Federal Drug Administration’s (FDA) voluntary guidelines for antibiotic use in food animals, as well as the standards of the USDA Organic certification programmeme.

"This very limited use of antibiotics is more restrictive than the new FDA Guidelines announced last December. We have yet to read any proposed legislation that we are not compliant with, and in fact, have been since 2008," said Dr Stewart-Brown.

"We listened to our consumers and we are proud to have developed a responsible programme that does not risk the medical effectiveness of antibiotics in human health, provides appropriate health care for animals and does not employ growth-promoting drugs," said Chairman Jim Perdue.

"While treating illness is a responsible part of animal care, we believe human-approved antibiotics should not be used to boost production or in place of responsible animal husbandry or hatchery management."

"This is not something that you simply turn a switch to implement," said Dr Stewart-Brown.

"Moving away from the conventional use of antibiotics in animal agriculture means more than taking human antibiotics out of your programmes. You have to develop programmes from breeder operations, through the hatchery and feed mill and onto the farm that are sustainable without that use. It takes a lot more effort with more stringent standards, but we believe this is what consumers expect from Perdue."

Perdue Foods started the move away from conventional antibiotic use in 2002, in response to growing consumer concern and our own questions about the practice.

"We recognised that the public was concerned about the potential impact of the use of these drugs on their ability to effectively treat humans," said Dr Stewart-Brown.

"We focused first on removing growth-promoting antibiotics." In 2005, the company phased out the use of specific medically important antibiotics in its feeds, including floroquinolones, four years before the FDA banned the use of floroquinolones in animal agriculture.

By 2007, the company had successfully removed all human antibiotics from its feed.

That same year, Perdue Foods launched the Harvestland brand, its no-antibiotics-ever product line.

"That was a major learning experience for us," said Dr Stewart-Brown. "No-antibiotics-ever was a very small part of the market, but it gave the opportunity to learn what it takes to successfully run such a programme. And we took those learnings and applied them across our entire company.

"We also found that it is not realistic or responsible to eliminate all antibiotics. No matter how carefully you raise animals, some are going to be exposed to infections that can only be treated with antibiotics. As veterinarians, we have a responsibility to properly treat those animals," said Dr Stewart-Brown.

"But, when we do treat chickens with antibiotics, we do it in a very focused and limited way that allows us to treat a single house and for the shortest duration possible, generally no longer than three days."