100% Complete & Balanced Nutrition for Adult Dogs. Mainstay delivers all the vitamins and minerals adult dogs need. Each nutritious serving provides high quality protein and all the vitamins, minerals and other essential nutrients adult dogs need on a daily basis. Plus, Mainstay is made with high quality ingredients. Mainstay delivers good nutrition you can always rely on, because it's a product backed by 70 years of Purina nutritional research. Great taste and great value! Your adult dog benefits from the 100% complete balanced nutrition and great taste - and you benefit from the great, affordable price. Mainstay proves that great taste and great nutrition don't have to be expensive. Animal feeding tests using Association of American Feed Control Officials (AAFCO) procedures substantiate that Purina Mainstay provides complete and balanced nutrition for maintenance of the adult dog. Selected Nutrients and Major Function: Protein-General Maintenance; Fat-Energy, skin, coat; Calcium-Bones, teeth; Potassium-Muscles; Sodium Chloride-Body fluids; Magnesium-Muscles, bones; Iron & Copper-Blood; Zinc-Skin; Iodine-Thyroid; Selenium-Muscles; Vitamin A-Eyes, skin; Vitamin D-Bones, teeth; Thiamine (Vitamin B1)-Digestion, nerves; Biotin-Skin, coat; Vitamin B12-Blood; Choline-Liver, nerves.