Effects of dietary arginine and lysine levels on growth performance, nutrient utilization and tissue biochemical profile of black sea bream, Acanthopagrus schlegelii, fingerlings

An 8-week feeding trial was conducted to determine the effects of imbalanced levels of arginine and lysine in the diets of black sea bream. Acanthopagrus schlegelii, fingerlings. Eight isonitrogenous diets were formulated using a combination of intact protein and crystalline amino acids to contain different arginine/lysine levels: 2.83/3.25, 3.46/4.06, 2.27/4.09, 3.51/2.70, 2.31/2.74, 2.87/4.03, 2.91/4.68 and 2.85/5.24, % dry diet (analysis values), respectively. Each diet was fed to triplicate groups of 25 fish (mean weight, 10.0 +/- 0.1 g) twice a day to apparent satiation. Fish fed diets with disproportionate levels of arginine and lysine showed significant (P<0.05) growth reduction compared to fish fed the control diet. The lower growth rates observed were due in part to lower feed intake, reduced nutrient availability (arginine and lysine), and increased catabolism of absorbed amino acids. Supplementing additional arginine to the diet was able to partially ameliorate the reduced growth, feed utilization and hepatic arginase activity observed in fish fed with excess dietary lysine, suggesting the possibility that there exists an antagonistic relationship between dietary lysine and arginine in black sea bream. Fish fed diets with excess lysine had lower whole-body protein content compared to fish fed the control diet. The significant increase in plasma ammonia levels as well as enzymes related to amino acid deamination and transamination reactions were found in the present study. To ensure optimal growth of black sea bream, the dietary levels of both arginine and lysine should be considered together when formulating feeds for this commercially farmed marine fish. (C) 2011 Elsevier B.V. All rights reserved.