Alleviative effect of biofloc technology (BFT) on extruded soybean meal (ESBM)-induced growth inhibition and intestinal barrier dysfunction in Rhynchocypris lagowskii

Abstract

This study evaluated the alleviative effect of bioflocs technology (BFT) on intestinal morphology, permeability, digestive function, immune function, antioxidant capacity and microbiota of Rhynchocypris lagowskii sensitized by extruded soybean meal (ESBM). In a 2 × 2 factorial design, R. lagowskii (6.40 ± 0.01 g) was randomly divided into 4 groups, which contains two culture modes (traditional mode and biofloc mode) and two levels of dietary ESBM (0% and 68%). At the end of the experiment (8 weeks), the results showed that the growth performance of R. lagowskii was significantly increased by BFT, but significantly decreased by feeding diets with 68% ESBM (P < 0.05). Culture mode significantly affected intestinal growth indexes, morphology, the levels of tight junction protein mRNA, the activities of digestive enzymes, immune function, inflammation response and antioxidant capacity in proximal intestines (PI), mid intestines (MI) and distal intestines (DI) (P < 0.05). These indexes (except fold height, lamina propria width, the levels of tight junction protein mRNA, the activities of protease, AKP and LZM, the levels of inflammation related mRNA, the levels of T-SOD and PC, the levels of Nrf2, Keap1, HO-1 and Maf mRNA in PI, the activities of CAT in MI, the activities of lipase and amylase in intestines) were also significantly affected the levels of dietary ESBM (P < 0.05). Intestinal permeability (DAO, 5-HT, ET-1 and D-LA) were only significantly affected by the levels of dietary ESBM (P < 0.05). In addition, the interaction between culture mode and the levels of dietary ESBM was observed for muscular layer thickness and T-AOC in PI, fold height, ZO-1, NF-κB and Nrf2 in MI, Claudin-2, IL-1β, TGF-β, T-AOC, Nrf2, HO-1 and Maf in DI (P < 0.05). Results of intestinal microbiota showed that relative abundance of Amaricoccus, Aquitalea, Chelatococcus and Nakamurella were significantly affected by culture mode, the levels of ESBM in diets and their interaction (P < 0.05). Therefore, this study indicated that intestinal morphology, permeability, digestive function, immune function, antioxidant capacity and microbiota in R. lagowskii could be affected by ESBM and alleviated by BFT.