Abstract
This study investigated the effects of different dietary arginine (Arg) levels on the growth, protein synthesis, antioxidant capacity, and immunity of postlarval mud crab Scylla Paramamosain . Six isonitrogenous and isolipidic diets were formulated to contain 1.51%, 1.81%, 2.16%, 2.35%, 2.73%, and 3.07% dietary Arg levels (dry matter). There were four replicates for each diet treatment (26 crabs per replicate, initial body weight: 7.40 ± 0.15 mg). After eight weeks of feeding trial, the survival and molting frequency (MF) of crabs were not affected by the experimental treatment ( P >0.05). Crabs fed the 2.50% Arg diet achieved the highest weight gain (WG) and specific growth rate (SGR) ( P <0.05). The whole-body protein content of the 2.16% and 2.73% Arg groups were significantly higher than that of the 1.51% Arg group ( P <0.05). Crabs in the 2.35% group obtained the highest levels of phenylalanine and leucine ( P <0.05). Superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) activity in the 2.16%, 2.35% and 2.73% Arg groups were significantly higher than that in other treatments ( P <0.05). Malondialdehyde (MDA) concentration and alkaline phosphatase (AKP) activity were not significantly affected by the treatments. The transcript levels of insulin-like growth factor 1 ( igf-1 ), rapamycinin ( TOR ), S6 kinase-polypeptide 1 ( s6k1 ) in crabs fed with 2.16% and 2.35% dietary Arg were significantly higher than those in crabs fed with 1.51% and 3.07% dietary Arg ( P <0.05). The lowest prophenoloxidase ( proPO ), relish , and lysozyme transcript levels were observed in crabs fed the 1.51% dietary Arg. The current study founded that the Arg requirement for postlaval S.paramamosain was 2.34% (5.20% of the dietary protein), based on the second order polynomial regression analysis of WG.