Decreased Immune-System Function
Throughout a dog's life, a process called peroxidation occurs. This is a normal process the body uses to destroy cells that outlive their usefulness and to kill germs and parasites, but this process also can destroy or damage healthy cells. As a dog ages, the damage caused by peroxidation accumulates and, in turn, increases the risk of certain problems such as infections.
Antioxidants are naturally occurring components in the body (but also can be acquired through diet). They help maintain overall health by neutralizing the peroxidation process of cellular molecules.
Research sponsored by IAMS™ found that dogs fed a diet rich in antioxidants such as vitamin E had improved immune responses and vaccine recognition. This might be especially important for mature/senior dogs, because IAMS research has found that, as dogs age, immune responses can decrease.
Deterioration of Skin and Coat Quality
Eating a complete and balanced diet with omega-3 fatty acids, such as those found in vitamin-rich fish oils, also helps rejuvenate dry skin and develop a healthy, lustrous coat.
More Frequent Intestinal Problems
Aging dogs might have higher numbers of unfavorable bacteria and lower numbers of beneficial bacteria in their intestines, which can result in clinical signs of gastrointestinal problems (such as diarrhea). A diet with a moderately fermentable fiber source such as beet pulp can help maintain intestinal health. Beet pulp provides energy for the cells lining the intestine and promotes proper stool formation.
How Do I Know When My Dog Needs a Mature Diet?
Different dogs show signs of aging at different times, and much of this variation is associated with size. Larger dogs generally appear mature/senior sooner than smaller dogs. The table below can show you when your dog should start a mature diet.
Dog Weight and Transition to Mature/Senior Foods
| Weight Range || Age to Begin Transition |
| More than 90 lbs || 5 years |
| 51 to 90 lbs || 6 years |
| 21 to 50 lbs || 7 years |
| Up to 20 lbs || 7 years |