McDonald's announced Wednesday that it plans to start serving chicken raised without human antibiotics at its U.S. restaurants.

McDonald's officials say the company will now require that its U.S. chicken suppliers stop routinely using antibiotics to treat their chickens within two years. 

"While McDonald's will only source chicken raised without antibiotics important to human medicine, the farmers who supply chicken for its menu will continue to responsibly use ionophores, a type of antibiotic not used for humans that helps keep chickens healthy," the fast food giant said in a statement.

Starting later this year, U.S. McDonald's restaurants will also begin serving low-fat white milk and fat-free chocolate milk from cows that are not treated with the artificial growth hormone rbST, the company said Wednesday.

The consumer advocacy group Illinois PIRG said it's pleased to see McDonald's taking steps to limit the use of antibiotics in chicken, saying the move will "signal to the marketplace a huge and growing demand for chicken raised without the routine use of antibiotics." However, the group is urging the fast food giant to "set a timeline for serving beef and pork raised without the routine use of antibiotics."

"With more than 23,000 Americans dying each year from antibiotic resistant infections, more must be done to stop the overuse of antibiotics in all meats," said Dev Gowda, an advocate with Illinois PIRG. "We're thrilled with the McDonalds' announcement today, but we don't want them to chicken out when it comes to setting a policy for beef and pork."