Impact of carbohydrate to lipid ratio and bile salts supplementation on performance, body gain and body composition of Nile tilapia fish

Abstract

A 8-weeks feeding trial was conducted to evaluate growth performance, body composition and some serum biochemical alteration of Nile tilapia fish fed three isonitrogenous and different energy level diets containing different levels of carbohydrates (40.1%, 34.9% and 29.9%) and lipids (6.1%, 10.6% and 16.1%) with carbohydrate-to-lipids (CHO/L) ratios 6.6, 3.3 and 1.86:1 respectively, without or with bile acids (BAs) supplementation (0.5g BAs/Kg diet) to make six experimental groups. Decreasing CHO: L ratio (from 6.6 to 3.3 or 1.86: 1) in Nile tilapia diet had no significantly effect on final body weight. Moreover, decreasing CHO/L ratio increased total body gain (TBG), gain% and SGR% in Nile tilapia diet, also numerically reduced feed intake and improved FCR, PER and EEU throughout whole experimental period. On the other hand, decreased CHO: L ratio from 6.6 to 3.3:1 with BAs supplementation increased final weight, TBG, gain% and SGR%, while lower ratio had no significant effect. Body lipid increased with lowering of CHO/L ratio and BAs addition in Nile tilapia fish diet increased whole body or hepatopancreas moisture or protein contents, while significantly reduced lipids content compared with fish group fed on the same diet without BAs supplementation. Serum total protein, globulin, total cholesterol, triglycerides and HDL concentrations increased before and after experimental challenge with decreasing CHO/L ratio while both ratio or BAs addition had no significant effect on serum creatinine, uric acid, GOT, GPT, total cholesterol, triglycerides and HDL concentrations before and after experimental challenge. High lipid diet (lower CHO/L ratio) improved immune response through increasing total WBCs count, phagocytosis, lysosomal activity before and after A. hydrophila experimental challenge and consequently reduced mortality%. The obtained data indicated that the optimum CHO/L ratio in Nile tilapia diet for maximum growth performance, better immune response and health condition is 3.30:1 with BAs supplementation.