Dietary arginine requirements of oriental river prawns (Macrobrachium nipponense) assessed using growth and biomarkers of antioxidant capacity

Abstract

An 8-week feeding trial was carried out to determine the dietary arginine requirement of oriental river prawns (Macrobrachium nipponense). Prawns of initial tank biomass (10.0 g) were fed isonitrogenic (ca 38% protein) and isolipidic diets (ca 7.5% lipid) with incremental concentrations of arginine (0.75, 1.19, 1.61, 2.02, 2.46, and 2.81%). The prawns were randomly assigned into 24 cylindrical polypropylene tanks (1000L), with 50 prawns in each tank replicated four times in a completely randomized design, and were fed three times daily to apparent satiation. Muscle samples were used to analyze the amino acid profiles. Hepatopancreas were collected for antioxidant activity and immune-related gene expression. The results indicated that the survival, growth performance and feed utilization were significant higher (p < 0.05) in prawns fed with 2.02% dietary arginine than in other treatments except the treatment with 2.46% dietary arginine. The highest biomass increase (25.5 ± 0.5 g), protein efficiency ratio (1.05 ± 0.08) and survival (87.0 ± 2.7%) were found in prawns fed with dietary 2.02%, and the lowest feed conversion ratio (2.53 ± 0.18) was observed in the same group. Whole-body crude protein content (15.4 ± 0.1%), lipid content (2.5 ± 0.1%) and muscle arginine content (1.47 ± 0.03%) significantly increased in prawn fed with dietary 2.02% arginine compared with other groups except dietary 2.46% arginine (p < 0.05). With increased dietary arginine supplementation up to 2.02%, the activities of hepatopancreas superoxide dismutase (25.07 ± 0.64 U/mg prot) and glutathione peroxidase (461.89 ± 8.79 U/mg prot) were increased (p < 0.05); nevertheless, the glutathione content (23.45 ± 3.47 μmol /mg prot) in the 2.02% dietary arginine group was similar with that of the control group (p > 0.05). Moreover, the hepatopancreas gene expressions of Toll-like receptor, dorsal, immune deficiency, and relish were significantly upregulated in the prawn fed with1.61% dietary arginine (p < 0.05). Broken-line, quadratic and cubic regression models are used to evaluate the optimal arginine requirements. The broken-line regression of biomass increase, based on the highest R2 value, showed that the optimum arginine requirement of oriental river prawns was 2.12% of dry matter (5.61% dietary protein). The optimum dietary arginine requirement, according to the cubic regression analysis for superoxide dismutase activity, was 2.27% of dry matter (6.01% of dietary protein). The ideal arginine concentration for antioxidant enzymes activity was thought to be higher than that for growth.