Carnitine is an essential growth factor for some insects, such as the mealworm (T. molitor). However, most insects and higher animals, as well as poultry, can synthesize carnitine. For common livestock species, there are no established nutritional requirements for carnitine. Recent studies have indicated that the biosynthesis of carnitine may be limited or inadequate in certain classes of humans and animals. No requirement data are available for poultry but some positive responses have resulted from carnitine supplementation. Supplemental L-carnitine at 50 mg per kg (22.7 mg per lb) has improved body weight gain and feed conversion and decreased abdominal fat of broilers (Iben and Meinhart, 1997; Rabie et al., 1997a, d; Rabie and Szilagyi, 1998). Egg quality and hatchability also have been favored by carnitine supplementation (Leibetseder, 1995; Rabie et al., 1997b, c).
