U.S. antitrust enforcers cleared Nestle SA's purchase of Ralston Purina Co. to create the world's largest pet food company after the firms agreed to divest two cat food brands to preserve competition. The U.S. Federal Trade Commission voted 4-to-0 to let the $10.1 billion deal proceed, with the two companies promising to sell Meow Mix and Alley Cat dry cat food brands to Hartz Mountain Corp., a unit of investment firm J.W. Childs Associates LE The merger would bring together such household names as Ralston's Dog and Cat Chow and Nestle's Friskies cat food and Mighty Dog brands.