Only the physiological L-carnitine should be used for fortification of diets. Oral doses of 100 to 150 mg per kg (45.5 to 68.2 mg per lb) have been used as supplementation doses.
The liver and kidney of mammals are able to synthesize carnitine from lysine and methionine; however, endogenous biosynthesis alone is not sufficient to keep carnitine concentrations at adequate levels (Duran et al., 1990). Nevertheless, pets receiving food with high amounts of animal products (e.g., meat and milk) should need no additional supplemental carnitine. Likewise, nursing puppies and kittens will be receiving sufficient carnitine, since milk is rich in the vitamin. The greatest concern for the need to supplement carnitine would be for dogs with DCM (sometimes of genetic origin) and for dogs that work rigorously and receive diets lacking in sufficient animal protein. In the working dog, L-carnitine increases aerobic capacity due to glycogen sparing effect, delaying onset of fatigue and hypoglycemia and decreasing production of lactic acid (Pelletier, 1992). After exercise, L-carnitine speeds up recovery. No information is available on the potential need of carnitine for cats.