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

Abstract

Objective: 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.