Don't put your pet on a senior food or a "light" diet just because it is at a certain age. Diets formulated with the older pet in mind frequently contain fewer calories, 18% less protein and 4% to 6% less fiber. Animals who will benefit from a diet with these characteristics are those with increased weight gain due to a decline in activity and those who suffer from frequent constipation.
The most frequent change in the aging pet is the slowing of the metabolic rate, which lowers the animals energy requirement. An animal who requires less energy but continues to eat at the same rate of energy intake stores surplus energy as fat and becomes overweight.
This obesity imposes an extra strain on the heart or any aged bones and joints. In this case, it would be helpful to feed the animal either less food or a food which contains a reduced amount of energy per unit of weight.
Likewise, the need for dietary protein may decline because of a change in activity, a slowing down of metabolic activity, and a diminished ability on the part of the kidneys to deal with the waste products of protein digestion. Such an animal would benefit from decreasing the total protein intake. The gastrointestinal tract loses tone with increasing age so the stimulative effects of added fiber may also be useful.
It must be emphasized that diets with the above characteristics may not be appropriate for an older pet who is still very active. Likewise, special conditions which are present in your pet may require a special diet.
Feed your pet according to its individual state and rate of activity. This can best be determined by first consulting your veterinarian and reviewing your pet's individual health and nutrient requirements.