Intestinal microflora of Litopenaeus vannamei using rice protein meal instead of fish meal

This study assessed the effect of rice protein meal replacement for fish meal on the growth, non-specific immunity, and disease resistance for juvenile shrimp Litopenaeus vannamei. Six groups of iso-nitrogenous and iso-lipid feeds named FM, R10, R20, R40, R60, and R80 were prepared by re-placing 0%, 10%, 20%, 40%, 60%, and 80% in FM protein with RPM, respectively, and then fed to shrimps. 720 healthy and evenly sized shrimps were allocated to 6 groups (3 repli-cates per group) and fed 4 times a day (7:00, 11:00, 17:00 and 21:00) for 8 weeks. Results revealed no significant differences in WG, FCR, and SGR of shrimps after replacing FM with 10% RPM . 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. CAT, ACP, and LZM were all significantly higher in the R10, R20, and R40 groups than in the FM group. GSH-Px activity in the R10 group was significantly higher than that in the FM group. 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 an-ti-lipopolysaccharide factor (alf) genes were significantly up-regulated in the R10 and R20 groups. The crustin a (cru a), immune deficiency (imd), and lysozyme (lzm) mRNA levels were sig-nificantly higher in the R10, R20, and R40 groups than in the other groups. The pro-phenoloxidase (PO) mRNA levels in the R20 group were significantly higher than those in the FM group. The replacement of 10%-40% of FM with RPM improved the gut flora composition of shrimps, increasing a beneficial bacteria (Bacteroidetes) abundance and reducing a harmful bacteria (Aspergillus and Vibrio) abundance. After the challenge test of Vibrio parahaemolyticus (7 days), the cumulative mortality in the R10 group significantly decreased. In conclusion, replacement of 10% FM by RPM significantly improved digestibility, protein synthesis, antioxidant capacity, and disease resistance in L. vannamei.