Only the physiological L-carnitine should be used for fortification of diets. Supplementation of 50 to 500 mg per kg (22.7 to 227 mg per lb) of diet have been used as supplementation doses for poultry. Although carnitine has been studied in humans and under laboratory conditions for many years, its effectiveness in promoting the performance and well-being of domestic animals has only recently received attention. A role for carnitine in swine and fish diets has been established and continued research may find that it has a place in the production of poultry and other livestock species. Some studies have found production responses for supplemental carnitine in poultry, while other reports have found no benefits.
Rabie and Szilagyi (1998) supplemented broiler diets with 50 mg per kg (22.7 mg per lb) of L-carnitine, which resulted in increased liveweight gain and improved feed efficiency. Weights of breast yield and thigh meat yield were increased, whereas quantity and percentage of abdominal fat were reduced by L-carnitine. L-carnitine fed to broilers at four levels from 0 to 150 mg per kg (0 to 68.2 mg per lb) improved weight gains and reduced abdominal fat (Rabie et al., 1997d). It was concluded that the effectiveness of supplemental carnitine for improving gains and (or) decreasing abdominal fat of broilers may depend on the age at which it is added. Under conditions of this study, L-carnitine at 50 mg per kg (22.7 mg per lb) of diet was effective.
A level of 50 mg per kg (22.7 mg per lb) of L-carnitine had positive effects on interior egg quality during the early stages of egg production (Rabie et al., 1997c). Leibetseder (1995) reported that L-carnitine in the feed of broiler breeder hens affected hatchability of chicks when given a conventional feed with L-carnitine at 0, 20, 50 and 100 mg per kg (0 to 45.5 mg per lb). After three weeks of feeding, hatchability increased by 4% and 2.9%, respectively, when L-carnitine was provided at 50 and 100 mg per kg (22.7 and 45.5 mg per lb). Carnitine in egg yolk was increased by the supplements.