Sandwich chain Subway will start serving antibiotic-free chicken and turkey at its U.S. restaurants next year, and within the next nine years will stop selling any meat from animals given antibiotics, the company said on Tuesday. Competitors such as Chipotle Mexican Grill Inc (CMG.N) and McDonald’s Corp (MCD.N) have announced similar supply-chain shifts, adding pressure on U.S. livestock producers to cut human antibiotics from their beef, hogs and poultry production.