Abstract:An eight week experiment was conducted to investigate the effects of dietary arginine on the growth performance, body composition, serum biochemical parameters, and liver enzyme activities of juvenile Korean rockfish (Sebastes schlegelii) and to determine the dietary arginine requirement. Six isonitrogenous and isolipidic diets were formulated to contain graded dietary arginine (1.5%, 1.0%, 2.0%, 2.5%, 3.5%, and 4.5% dry diet). The crystalline amino acid mixture was supplemented in the test diets to simulate the amino acid profile of the juvenile S. schlegelii muscle protein, except for arginine. The initial average body weight of the juvenile S. schlegelii was (12.03±0.03) g. The results showed that, with increasing dietary arginine, the weight gain rate (WGR), specific growth rate, and protein efficiency ratio significantly increased at first and then decreased; these were significantly higher in the 2.34% and 2.80% arginine diets than the 1.39% arginine diet, but the feed conversion ratio showed the opposite trend. The crude protein content of the muscle was significantly affected by dietary arginine levels and was significantly higher in the 2.34% arginine diet than the other groups. The concentrations of both total essential amino acids and total amino acids first increased and then decreased in the whole fish and muscle tissues. The levels of albumin and nitrogen oxide in the serum significantly increased first and then decreased (P<0.05), whereas the serum blood urea nitrogen content first increased and then plateaued. However, the glutamic pyruvic transaminase in the serum significantly decreased at first and then increased, and was significantly lower in the 2.34% arginine diet than in other groups. The activities of superoxide dismutase, lysozyme, aspartate aminotransferase, total antioxidant enzymes, alkaline phosphatase, total nitric oxide synthase, and inducible nitric oxide synthase in the liver first significantly increased and then decreased, whereas the content of malonaldehyde first significantly decreased and then increased. With WGR as an evaluation index, the optimal arginine requirement of juvenile S. schlegelii was 2.78% (5.56% dietary protein).
