In the senior years of your dog’s life, they tend to slowdown in their activity level as well as their metabolism. For these reason, their caloric intake can decrease sometimes as much as 25 to 35 percent. Some causes for slowing down in their activity level can be due to aging of the joints including arthritis. Similar to the aging process in humans. Therefore the objective of feeding a geriatric dog would be to promote health while providing joint support. And with that said, maintaining a normal body weight can slow if not prevent further development of such problems that come with aging.
A food that contains high quality ingredients as well as a highly digestible protein should be chosen. Also a human grade supplement should be added, to help support good joints and aid in reducing inflammation. Some such supplementation that I would suggest would be Glucosamine and Chondroitin Sulfate. Be sure to use the proper amount based on body weight.
Caloric needs will greatly vary as energy needs are vastly different with each elderly dog. Activity levels are never the same. Just Monitor intake and adjust the amount being fed to prevent obesity. High quality protein is important as their lean body mass will decrease with the aging process. This results in a loss of their protein that they will have in their reserves. These reserves are extremely important during times of dealing with any stress or any type of illness. So protein calories should be lower than say a puppy would need for growth requirements, but more than is required for an adult maintenance diet. Also note that when reducing fat in an older dogs diet, be sure that the fat remaining is rich in essential fatty acids.