Positive impacts of dietary prebiotic inulin on growth performance, antioxidant capacity, immunity, and intestinal microbiota of red swamp crayfish ( Procambarus clarkii )

Inulin is known to be a prebiotic used in aquatic animals. However, no investigation has been conducted to evaluate its effect on freshwater crayfish. In this study, a 7-week feeding trial using diets supplemented with inulin (0.0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% feed) was conducted on 360 red swamp crayfish ( Procambarus clarkii ) (initial body weight 6.58 ± 0.16 g) with four parallels each group, in order to determine the effects of dietary inulin on the growth performance, antioxidant capacity, immune response, and intestinal microbiota of this crayfish. Firstly, the feeding trials showed that the survival rate and growth performance of P. clarkii fed 0.6% dietary inulin were significantly improved and feed conversion ratio was significantly reduced. Secondly, the antioxidant capacity of hepatopancreas was significantly improved by inulin supplementation. The crayfish fed 0.6% dietary inulin had the lowest malondialdehyde content and the highest antioxidant enzyme (T-AOC, T-SOD, GSH-PX, and CAT) activities. The addition of 0.6% and 0.8% dietary inulin significantly increased the expression levels of immune-related genes in the intestine and hepatopancreas. Moreover, high-throughput sequencing of 16S rRNA showed that 0.6% dietary inulin altered the beta diversity and composition of the intestinal microbiota, with a significant increase in the relative abundance of the Citrobacter spp. Meanwhile, intestinal microbial KEGG pathway analysis showed that 0.6% dietary inulin promoted metabolism, digestion, transport, circulation, and cellular processes in P. clarkii . This study indicated that 0.6% dietary inulin was appropriate for P. clarkii to improve the growth, antioxidation, immunity, and intestinal health.