Alterations of amino acid metabolism and intestinal microbiota in Chinese mitten crab (Eriocheir sinensis) fed on formulated diet and iced trash fish.

Formulated diet (FD) and iced trash fish (ITF) are common diets during E. sinensis farming. However, whether FD can completely replace ITF during long-term E. sinensis farming is still unclear. Thus this study was conducted to compare the differences in amino acid metabolism and intestinal microbiota of the E. sinensis fed on different diets. The crabs were randomly divided into three groups fed on FD, ITF and mixed diet (MD, FD: ITF = 1:1), respectively. The results showed that there were no significant differences in amino acid composition among FD, MD and ITF groups. The activities of AST and ALT, and the mRNA levels of amino acid metabolism-related genes were significantly up-regulated in FD or/and MD groups compared with ITF group. The diversity of intestinal bacterial community was similar between the FD and ITF groups, but the relative abundance of dominant taxa showed marked differences between the two groups. At the phylum level, the relative abundance of Firmicutes was significantly higher, but the relative abundance of Proteobacteria was significantly lower in the FD group than that in ITF group. Meanwhile, at genus level, the relative abundance of Candidatus_Hepatoplasma in FD was higher than that in ITF group. Data related to functional prediction demonstrated that the significantly differenced pathways between the two groups were observed in metabolism (Pyrimidine metabolism, Glycolysis/Gluconeogenesis and Citrate cycle) and environmental information processing (transporters). The overall results indicated that replacement of ITF by FD did not affect amino acid composition, but altered amino acid metabolism and the relative abundance of intestinal microbiota. Our data provided a valuable reference for FD application replacing ITF during long-term E. sinensis farming.