CHIPOTLE MEXICAN GRILL, $661.95, symbol CMG on New York, offers higher-quality food and better decor and service than many fast-food chains, and charges slightly higher prices. Under its Food with Integrity initiative, it uses naturally raised meat wherever possible. The company’s all-natural meat comes from animals that are raised humanely, never given antibiotics or hormones and fed a vegetarian diet. In January 2015, the company halted sales of pork items at one-third of its nearly 1,800 U.S. restaurants after learning that a key supplier had failed to meet its pig-housing standards. Under Chipotle’s requirements, pigs must be housed in humane conditions with access to the outdoors, rather than in pens. Chipotle uses pork in around 7% of the burritos, tacos, bowls and salads it sells. After suspending this supplier, the company began rotating carnitas on and off of menus in various markets for about six weeks at a time. But this caused customer confusion about where and when pork would be available. Chipotle…