Dietary crude protein concentrations and L-carnitine inclusions interactively influence performance parameters of grower broiler chickens offered sorghum-based diets

Abstract

This study investigated the effects of dietary crude protein (CP) and L-carnitine on the performance of broiler chickens offered sorghum-based diets. In a 3 x 3 factorial array of CP concentrations (220, 190, 160 g/kg) and L-carnitine inclusions (0, 75, 150 mg/kg), dietary treatments were offered to 324 off-sex, male Ross 308 broiler chickens from 7 to 33 days post-hatch. Treatment interactions (P < 0.001) were observed for growth performance parameters with 75 and 150 mg/kg L-carnitine inclusions in 160 g/kg CP diets increasing weight gain by up to 15.9 % (1593 versus 1374 g/bird), feed intake by up to 12.4 % (2492 versus 2218 g/bird) and improved FCR by up to 3.16 % (1.564 versus 1.615). In contrast, L-carnitine inclusions in 230 and 190 g/kg CP diets had negligible impacts on growth performance. Reducing dietary CP compromised growth performance and increased relative abdominal fat-pad weights by 44.1 % (11.44 versus 7.94 g/kg) as main effects but L-carnitine did not influence fat-pad weights. The possibility that growth performance responses observed in birds offered 160 g/kg CP diets may be attributed to L-carnitine counteracting the effects of NH3 intoxication which is given consideration because it has been established that L-carnitine is protective against (NH3) toxicity. Reducing dietary CP significantly increased jejunal and ileal digestibility coefficients of the majority of amino acids; whereas, L-carnitine had negative effects. Also, L-carnitine significantly depressed free plasma concentrations of 13 amino acids but increased concentrations of lysine, methionine, valine and glutamine. The possibility that L-carnitine was competing with amino acids for intestinal uptakes is discussed.