Effects of Supplementation Coated Lysine and Methionine in Mixture Protein Diets on Growth Performance, Digestibility and Serum Biochemical Indices of Juvenile Black Sea Bream, Acanthopagrus schlegelii

摘要

Four experimental diets were formulated to evaluate the effect of coated lysine (Lys) and methionine (Met) supplemented in mixture protein diets of juvenile black sea bream, Acanthopagrus schlegelii. Fish meal (FM) was the main protein source in control diet, and 21.2% FM was replaced by the mixture of soybean protein concentrate, meat and bone meal, and monosodium glutamate protein in replacement diets with coating Lys and Met were suppled at none (0%, 0%), low (1.7%, 1.1%) and high (5.0%, 3.4%) level (designated as NLM, LLM and HLM diet, respectively). Each diet was fed to triplicate groups of 20 fish (initial mean weight, 4.13±0.16 g) twice a day to apparent satiation for 8 weeks, in a flow-through system. Results showed that amino acid supplementation significantly improved weight gain and specific growth rate in these mixture protein diets groups, and the fish fed with HLM diet showed comparable growth with the control group. Feed efficiency ratio (FER), protein efficiency ratio (PER), and crude protein and Met content in dorsal muscle were significantly affected by diet amino acid level. The highest apparent digestibility coefficients appeared in HLM group but the values showed insignificant difference with the control group. Serum activities of aspertate aminotransferase and alanine aminotransferase in control group were lower than those of in other treatments. Fish fed with NLM and LLM diets had higher triglycerides concentration than those of fed the HLM and FM diets. Furthermore, the feed cost of the various feed treatments were evaluated, and the three test diets were all lower than the control diet. The present study indicated that 21.2% FM in black sea bream diet can be successfully replaced by mixture protein with sufficient coated Lys (5.0%) and Met (3.4%) supplemented.