Dogs with liver disease have different dietary needs then a healthy dog. Depending on the severity of liver disease in dogs, the percentage of protein that they need and can tolerate is variable. The liver makes different proteins, such as clotting factors and albumin, so dietary protein is very important to maintain liver function. However, if a dog has liver failure, then too much dietary protein can cause hepatic encephalopathy (neurologic impairment secondary to liver failure). Signs of hepatic encephalopathy in dogs are acting lethargic, spacey, star gazing, and possibly seizures or blindness. Prescription liver diets have less protein then an adult maintenance diet but the protein is very high quality and digestible.
Dogs with copper storage liver disease due to a genetic abnormality or cholestatic liver disease require a prescription liver diet. The primary changes in the diet that are beneficial are a reduced level of copper and an increased level of zinc. The reduced dietary copper helps lower the copper level in the liver which causes oxidative stress and damage. The increased dietary zinc can reduce copper uptake from the intestinal tract, thereby reducing copper liver levels even further.
Some other nutrients that are added or reduced in prescription liver diets are the following: Vitamin E and C for antioxidant effects. The liver is sensitive to oxidative damage and antioxidants can be protective to the liver cells. L-carnitine is an amino acid which is important in maintaining normal fat metabolism in the liver. Sodium levels are reduced to minimize fluid retention that can occur in dogs with liver failure.
Prescription liver diets can be purcahsed from your veterinarian, or from some pet food stores or websites with an appropriate prescription.