Effect of protein reduction with indispensable amino acid supplementation at different levels in practical diets of Nile tilapia (Oreochromis niloticus) fish.

Abstract

To estimate the effect of reducing dietary protein levels in Nile tilapia (Oreochromis niloticus) with dietary supplementation of commercially available synthetic amino acids at different levels on growth performance, whole-body composition, morphometric indices, and serum metabolites. Design: Randomized controlled experimental study. Animals: One hundred eighty male Nile tilapia fingerlings. Procedures: One hundred eighty male Nile tilapia fingerlings were equally distributed in twelve glass aquaria (15 fish per aquarium) and fed the formulated diets at 4-5% of the body weight. Every two weeks, tilapia was weighed, and the amount of feed intake was adjusted according to the increase in the tilapia weight. Results: By reducing dietary protein levels to 26%, final body weight (FBW), weight gain (WG), weight gain percent (WG %), specific growth rate (SGR), protein efficiency ratio (PER), and feed intake (FI) were significantly reduced, while feed conversion ratio (FCR) was significantly increased. Indispensable amino acid (IAA) supplementation at 120% of the NRC requirements to low protein diets (26 and 28%) resulted in a significant improvement in all growth performance parameters. The reduction of dietary protein to 26% resulted in a significant increase in triglycerides (TG), cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine concentrations. Serum IgG, IgM, and reduced glutathione (GSH) showed a significant improvement with IAA supplementation at 120% of the NRC requirements. Conclusion and clinical relevance:Dietary protein level could be lowered to 26% with supplementation of IAA at 120 % of the NRC recommendation to maintain comparable growth performance of Nile tilapia.