Similar to healthy dogs, sick dogs need to eat in order to supply energy and nutrients for growth, for replacement and repair; as well as to meet an ever changing need. Nutritional requirements for a sick dog usually do not differ greatly from those of a healthy dog. A sick dog's dietary needs, however, can become substantially different from those of a healthy dog.
Diseases in which a dog's diet will need to be changed are often due to true nutritional diseases, in which the diet itself is responsible for the disease. Most of the true nutritional diseases are deficiency diseases. What this means is that they are diseases caused by a diet that contains an insufficient amount of one or more needed nutrients. Most of these diseases were the result of inadequate or improperly balanced home-made food. Since cost-effective commercial food became more and more nourishing, most of these deficiency diseases gradually disappeared. Vitamin or mineral deficiencies are rarely seen as a primary disease any more. Both vitamins and minerals are inexpensive and are needed in such small amounts that today, few commercial dog foods fail to contain them in adequate amounts.
Although energy and protein continue to be a problem with some dog foods, the number of brands that still contain insufficient fat or poor quality, indigestible protein become less and less every year. When a deficiency of fat occurs, it most often appears as an insufficient amount of total energy in the diet which results in weight loss, sluggishness, dry and dull hair coat, poor physical condition and, in some extreme cases, emaciation and uncontrolled diarrhea. A deficiency of essential fatty acids may also occur, although it is unlikely. The total amount of the fats most often used in commercial foods can drop to as low as 1% of the diet and that diet will still contain sufficient fatty acids. The only exception to this might be in cases of dry foods where larger quantities of fat have turned rancid.
When a deficiency of fatty acids does occur, it appears as a loss of weight and condition, a dry, dull coat, but more specifically as eroded areas on the skin. These will most likely show on the pads of the feet, between the toes and over the bony protuberances of the body where pressure reduces the blood supply. Although these erosions may superficially resemble "hot spots," they differ from them in four major aspects such as: They do not respond to routine steroid therapy; they appear on both short-haired as well as long-haired dogs; they require an average of three months to heal; and adding fatty acids to the diet promotes their recovery, because a deficiency of fatty acids caused them.
A deficiency of protein in the diet is still sometimes seen. This causes weight loss and dull, dry hair coats. It may also produce anemia, reduce the body’s ability to cope with and recover from infections, and, if left neglected, will eventually lead to the dog’s death.
