Physiological condition, rather than chronological age, determines whether a dog is mature. Aging begins when the body's systems start to slow down, when cells deteriorate faster than the body can repair them. Though large breeds tend to age faster than smaller breeds, the mature years generally begin at around 7 years (5 years for large breeds). If you feed your dog a diet designed to address the nutritional needs of his age, you can best maintain his overall health and well-being.
As your dog ages, it is important to detect and address with his veterinarian the telltale signs of aging or disease: a dull, dry coat and flaky skin, joint stiffness, energy loss, weight gain, increased water intake, digestive problems, and frequent constipation. These signs, among others, may be caused either by normal wear-and-tear or perhaps by the onset of disease. In any case, detecting and addressing them early may give your dog a greater chance to stay active and healthy.
When and how your dog responds to the aging process has a lot to do with genetics and environment, but nutrition plays an equally important role. The quality of food and its ability to maintain and nourish your dog's cells can help promote a long, healthy life.
As your dog ages and his systems become less efficient, he relies increasingly on the food you provide to make up for his body's shortfalls. According to Michael Hayek, PhD, an IAMS research nutritionist who specializes in geriatric nutrition, "Aging dogs need the same nutrients as younger dogs; however, the quantity or the way the nutrients are provided may change."