NEW YORK – Wal-Mart, the nation’s largest food retailer, is urging its thousands of U.S. suppliers to curb the use of antibiotics in farm animals and improve treatment of them.

That means asking meat producers, eggs suppliers and others to use antibiotics only for disease prevention or treatment, not to fatten their animals, a common industry practice. Experts say Wal-Mart is the first major retailer to take a stance to limit the use of the antibiotics.

The guidelines also aim to get suppliers to stop using sow gestation crates and other housing that doesn’t give animals enough space. They’re also being asked to avoid painful procedures like de-horning or castration without proper pain management.

The push is part of an industry trend responding to shoppers who want to know more about where their food comes from and who are choosing foods they see as more healthy or natural. It comes after activists have reported animal abuse at farms supplying Wal-Mart and other major companies.

Wal-Mart wants its suppliers to produce annual reports on antibiotic use and their progress on animal welfare and post the reports on their own websites. It’s also pressuring suppliers to report animal abuse to authorities and take disciplinary action.

Kathleen McLaughlin, senior vice president of Wal-Mart’s sustainability division, told the Associated Press in a phone interview Thursday that the retailer is not putting deadlines on suppliers and the steps aren’t mandatory.

Still, Wal-Mart’s size gives it outsized influence on its suppliers’ practices, and changes it pushes can affect products at all stores. For example, when Wal-Mart asked its suppliers to reduce packaging about a decade ago, it spurred innovations in the consumer products industry. For example, Procter & Gamble introduced tubes of Crest toothpaste that could be featured upright on shelves without boxes.