Abstract
Four diets were prepared to include a mixture of medium-chain fatty acids and taurine as a digestive/ metabolic enhancer (DME, AQUAGEST®) at 0, 1, 2, and 3 g DME/kg diet and fed to common carp (initial weight, 4.55±0.03 g) for 70 days. Dietary DME significantly increased the final weight, weight gain, specific growth rate, feed intake, and protein efficiency and decreased feed conversion ratio in a dose-dependent manner (P<0.05). The body lipid composition was significantly improved by feeding DME at 2 g/kg diet (P=0.0141). The intestine villus length and the number of goblet cells were significantly increased in fish fed 2 g DME/kg diet (P<0.05). The intestinal villi displayed increased length, branching, and density by supplementing DME to common carp diets. Fish fed DME at 2 g/kg diet displayed markedly decreased aspartate aminotransferase (AST) and alanine aminotransferase (ALT ) (P=0.025 and P=0.043) and increased total protein and globulin (P =0.002 and P=0.003). Additionally, fish fed 2 and 3 g DME/kg levels displayed significantly increased albumin levels (P=0.006). Lysozyme and phagocytic activities were increased by feeding DME at 2 g/kg diet, while the phagocytic index increased by 2 and 3 g/kg diet (P<0.05). The optimal supplementation level of DME is 1.63 to 2.05 g/kg for common carp based on the polynomial regression analysis. In conclusion, common carp fed diets with a mixture of medium-chain fatty acids and taurine displayed improved growth, digestion activity, and immune response.