Monascus Purpureus M-32 Fermented Soybean Meal Improves the Growth, Immunity Parameters, Intestinal Morphology, Disease Resistance, Intestinal Microbiota and Metabolome in Pacific White Shrimp (litopenaeus Vannamei)

Monascus purpureus M-32 was successfully isolated from the Chinese traditional food red mould rice, and its fermentation product was supplemented in the diet of Litopenaeus vannamei at different concentrations (T0: 0 g/kg; T1: 5 g/kg; T2: 10 g/kg and T3: 20 g/kg). After 8 weeks, the dietary administration of the M-32 fermentation product significantly decreased the FCR in groups T1 and T2 and significantly increased the SR in group T3 compared to those in the control (T0) (P < 0.05). The hepatopancreatic amylase (AMS) activity of group T2 was significantly higher than that of the control group (P < 0.05). The antioxidative activity was evaluated by determining GSH-Px, SOD and T-AOC activities and MDA levels, and the results indicated that supplementation with the M-32 fermentation product significantly improved GSH activity and reduced the MDA level (P < 0.05). The analysis of immune parameters showed that the activities of AKP and LYZ increased significantly in shrimp fed the M-32 fermentation product (P < 0.05). Intestinal histological observations demonstrated that M-32 could significantly improve the intestinal morphological structure, including measures such as villus height, villus width, and muscular thickness (P < 0.05). Microbiota analysis showed that the M-32 fermentation product modulated the intestinal microbial composition, and the relative abundance of Lactobacillus increased significantly in shrimp fed with M. purpureus. Principal coordinate analysis (PCoA) and non-metric multi-dimensional scaling (NMDS) analysis showed that the gut microbiota of groups T1, T2 and T3 was significantly different from that of the control group. Additionally, the supplementation of the M. purpureus fermentation product enhanced the resistance of the shrimp against V. parahaemolyticus infection. In conclusion, the use of M. purpureus strain M-32 as a feed additive was beneficial to L. vannamei by promoting growth performance, the immune response, intestinal health and disease resistance.