APPLICATION OF IDEAL PROTEIN CONCEPT ON DIETARY PROTEIN REDUCTION IN NILE TILAPIA DIETS Oreochromis niloticus

Using of the ideal protein concept in aquaculture feed formulation aim to provide the exact balance of amino acids to cover fish requirements required for optimal growth and maximum production which lead to a reduction of dietary protein content, decreasing production costs in intensive fish farming and overcoming environmental pollution which resulted from nitrogenous products of protein metabolism. the present investigation was carried out for evaluation the effects of using ideal protein concept on reduction of dietary protein content for Nile tilapia (Oreochromis niloticus) with supplementation of synthetic commercial amino acids on growth performance response, whole fish body composition, level of some serum metabolites, morphometric index, intestine and muscles health and feeding costs of unit of weight gain of the Nile tilapia juvenile.

Three hundred juvenile Nile tilapia (6.3 g average body weight) were randomly divided into 5 groups, 3 replicates for each with 20 fish per experimental unit. The fish were reared in glass aquaria equipped with continuous air flow and fed five [32 CP (NRC1993), 28.5, 26.5, 24.5 & 22.5 % digestible protein] isocaloric (3000 Kcal DE/Kg) and digestible isolysine diets ad libitum 4 times a day for 12weeks. The synthetic amino acids were added at levels to meet the amino acid profile of the control diet.

Fish were weighed and counted biweekly to measure growth performance (average body weight, body weight gain) and feed utilization (feed consumption, feed conversion ratio & protein efficiency ratio). At end of the experiment, 6 fish were randomly obtained from each group for whole body proximate chemical analysis. At end of experiment 6 fish/ group were anaesthetized with tricaine methanesulphonate (MS-222) to collect nonheparinized and heparinized blood samples for determination of total protein, albumin, total immunoglobulin, triglycerides, liver enzymes, Urea & Creatinine, hemoglobin (Hb), hematocrit (Ht) and blood cell counts and to obtain weights of whole body, liver, viscera, intraperitoneal fat, dressed carcass and fillet. For histopathological examination, intestine and muscle samples were taken and fixed in 10% neutral buffered formalin for microscopic examination of the intestinal fold, enterocyte, microvillus height and muscle fiber diameter.

The growth data (final weight, weight gain, feed conversion and feed intake) revealed that fish groups which fed experimental diets based on digestible amino acids (28, 26, 24% digestible protein) showed better growth and weight gain than fish fed experimental diet based on total amino acids profile according to [32% crude protein (NRC1993)]. Also, it was concluded that is possible to reduce the dietary protein from 28 to 24% digestible protein for juvenile Nile tilapia based on ideal protein concept.