Effect of Rice Protein Meal Replacement of Fish Meal on Growth, Anti-Oxidation Capacity, and Non-Specific Immunity for Juvenile Shrimp

This study assessed the effect of rice protein meal replacement for fish meal on the growth, nonspecific immunity, and disease resistance on juvenile shrimp Litopenaeus vannamei. Six groups of iso-nitrogenous and iso-lipid feeds named FM, R10, R20, R40, R60, and R80 were prepared by replacing 0%, 10%, 20%, 40%, 60%, and 80% in FM protein with RPM, respectively, and then fed to the shrimps (0.54 ± 0.01 g). An amount of 720 healthy and evenly sized shrimps were allocated to six groups (three replicates per group) and fed four times a day (7:00, 11:00, 17:00 and 21:00) for eight weeks. Results revealed no significant differences in WG, FCR, and SGR of shrimps after replacing FM with 10% RPM (p > 0.05). In the R10 and R20 groups, SOD and T-AOC activities were significantly higher than those in the FM group, whereas the opposite was observed for MDA content (p < 0.05). CAT, ACP, and LZM were all significantly higher in the R10, R20, and R40 groups than in the FM group (p < 0.05). GSH-Px activity in the R10 group was significantly higher than the activity in the FM group (p < 0.05). AKP, PO, TYS, GPT, and GOT activities were significantly higher in the R10 group than in the FM group (p < 0.05). Compared to the FM group, the eukaryotic translation initiation factor 3K (eif3k) gene was significantly up-regulated in the R10 group, whereas the penaiedin 3a (pen 3a) and anti-lipopolysaccharide factor (alf) genes were significantly up-regulated in the R10 and R20 groups (p < 0.05). The crustin a (cru a), immune deficiency (imd), and lysozyme (lzm) mRNA levels were significantly higher in the R10, R20, and R40 groups than in the other groups (p < 0.05). The prophenoloxidase (PO) mRNA levels in the R20 group were significantly higher than those in the FM group (p < 0.05). The replacement of 10−40% of FM with RPM improved the gut flora composition of shrimps, increasing beneficial bacteria (Bacteroidetes) abundance and reducing harmful bacteria (Aspergillus and Vibrio) abundance. After the challenge test of Vibrio parahaemolyticus (7 days), the cumulative mortality in the R10 group significantly decreased (p < 0.05). In conclusion, replacement of 10% FM by RPM significantly improved digestibility, protein synthesis, antioxidant capacity, and disease resistance in L. vannamei.