Medical Management International (MMI) has the best interests of our furry and feathered friends at heart. As the world's largest pet-specific veterinary hospital operator, the unit of candy giant Mars provides medical services and procedures for pets through clinics in more than 900 PetSmart stores. Under the "Banfield, The Pet Hospital" name, it employs more than 3,200 veterinarians. It also operates about a half a dozen veterinary hospitals in Canada. In addition to its hospital business, MMI offers pet wellness plans, which provide discounts on preventive care (such as vaccinations and annual exams) and other veterinary services. The company is 21%-owned by pet products retailer PetSmart.