CHICK-FIL-A, America’s largest fast-food chicken sandwic1h chain, has announced its entire supply chain is now antibiotic-free.

It is the first major chain in the US to meet this target, after announcing in 2014 it would have removed antibiotics from its supply chain by the end of this year.

In mid-September, the company announced it had met the target in May this year, ahead of schedule.

The withdrawal includes antibiotic treatments for any reason through feed, water or via vaccines, and also outlaws the use of ionophores.

Birds that need antibiotics will be treated but are then removed from the Chick-fil-A supply chain and sold elsewhere.

The restaurant said it had introduced a strict verification system, with suppliers having to be re-certified annually as antibiotic-free.

“We know consumers care about how their food is made and where it comes from, including the use of antibiotics. Because it was important to our customers, it was important to us,” said Matt Abercrombie, director of menu and packaging. “Chick-fil-A has always been committed to serving customers delicious food made with high-quality ingredients and offering No Antibiotics Ever chicken was the next step.

“Our goal was to pursue the highest standard and partner with the USDA to verify it.”

The chain has more than 2,400 restaurants in the States and is famous for its fried chicken sandwiches. It is on track to become the third-largest fast-food chain in the United States.