NEW YORK — Wal-Mart's push to get its suppliers to give farm animals fewer antibiotics and more room to roam is expected to have a big impact on the food industry, experts say. Though the steps are voluntary, Wal-Mart, which sells more food than any other store, has a history of using its retail muscle to change the way products are made and sold across the retail industry. Wal-Mart told The Associated Press that it's 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.