Chicago ? McDonald’s Corp. said Thursday it was directing its meat suppliers worldwide to phase out the use of growth-promoting antibiotics in animals because of concerns that the practice lessens the drugs’ effectiveness in humans.

McDonald’s is the first major fast-food chain to take such a step.

The decision by the world’s biggest restaurant company came after a year of consultations with environmental, science and consumer groups that had pushed for cutbacks. Those organizations hope the move by one of the largest meat buyers marks a turning point in the way U.S. farmers raise animals.

The policy does not prohibit the use of antibiotics to treat sick livestock. It is aimed instead at antibiotics routinely given to animals to promote growth.

McDonald’s is telling its direct suppliers — those that control all stages of animal production — to phase out such antibiotics by the end of 2004. Direct suppliers provide most of McDonald’s poultry and 20 percent of its meat. The Oak Brook, Ill.-based company also is offering incentives to indirect suppliers of beef and pork.

Doctors are increasingly confronting germs that have become antibiotic-resistant. Many scientists think the overuse of antibiotics in humans and livestock is causing many drugs to lose their effectiveness by speeding the rate at which bacteria become resistant.

The animal drug industry, however, argues that using antibiotics on farm animals makes food safer.