It is a common thing for senior dogs to go through some changes and are usually prone to various kinds of diseases. Because of old age, a senior dog food may be changed. If the dog is healthy, there may be no need for the change of food, but if otherwise, the food needs to be changed. Senior dogs do not have any best food. There is always a different food requirement for every dog. A diet that works best for one dog may not work for another. Every dog with it owns nutrients requirement.