Man’s best friend, the dog, and especially the aging dog, frequently displays behavior that can be interpreted as fatigue. Lack of energy and stamina is implied when there is noticeable slowing of mobility and a decrease in the duration and vigor of play activities. This apparent diminution of vitality is frequently associated with increased sleeping and, possibly, a lessening of appetite and general responsiveness. These features are not normal in puppies and adolescent dogs, and when they occur, they frequently trigger an investigation to search for an underlying health problem such as a nutritional or hormonal deficiency, cancer, or cardiovascular malfunction. In contrast, The signs associated with fatigue are usually observed in older animals and are expected to become more and more pronounced as an animal enters into its senior years. In fact, the signs are so common that they are considered to be an expected part of the aging process manifested by a generalized deterioration including fur quality, posture, joint motion, circulatory and nervous system function, etc. Largely depending upon the genetic makeup, the progressive decline may become noticeable at approximately 4 to 7 years in the average animal prompting a vigilant search for treatable problems in order to maintain maximum health and activity. Even after implementation of special diets and optimal care rendered by health professionals, owners observe their pets to continue to loose energy and the ability to participate in a fully active life.