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

Document Type : Original Articles


1 Department of Nutrition and Nutritional Deficiency Diseases, Faculty of Veterinary Medicine, Mansoura University, 35516 Egypt.

2 Faculty of Veterinary Medicine, Mansoura University, 35516 Mansoura, Egypt

3 Department of Animal Nutrition, Faculty of Veterinary Medicine , Mansoura University, Mansoura 35516, Egypt


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 were 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.


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