Natura Pet Products Inc. offers Chicken Meal & Brown Rice Formula Senior dog food in its California Natural limited ingredient line. Specifically formulated to meet the needs of aging dogs, the food is high in protein, has less fat and includes L-carnitine to help maintain muscle mass and lean body weight, according to the company. Glucosamine, chondroitin sulfate and long-chain omega-3 fatty acids also are included in the senior formula.