Effects of dietary probiotics supplements on the growth performance, antioxidant capacity, and intestinal health of juvenile Eriocheir sinensis

Probiotics is a promising solution for the green development of Eriocheir sinensis industry. To screen potential probiotics for E. sinensis, we investigate the role of dietary Lactobacillus parafarraginis (LP group), Bacillus subtilis (BS group) and their complexes (LB group) on the growth, molt, immunity and intestinal health of juvenile crab. After feeding for 28 days, we found a significant increase in body weight of probiotic group, with the highest in the LB group. ecdysone was significantly higher in the LB group, which in turn increased its growth efficiency. Probiotics significantly increased the antioxidant capacity and decreased MDA and aminotransferase levels. Probiotic complexes improved PO activity in E. sinensis and showed better immune performance. Interestingly, the relative abundance of potential pathogenic microorganisms Candidatus Bacilloplasma and Vibrio was reduced in the probiotic group. Protomicrobiota in the gut such as Tyzzerella, Pseudorhodobacter in BS, Coprobacillus, Rhodobacter in LP and unclassfied, ZOR006 in LB showed higher abundance. Probiotics protected the intestinal health and enhanced the immunity of E. sinensis by maintaining the abundance of protomicrobiota in the intestine and reducing the abundance of potential pathogenic bacteria. On the other hand, probiotics positively affected juvenile crab by regulating metabolic pathways such as cGMP PKG signaling pathway, mTOR signaling pathway, ABC transporter protein, and protein digestion and absorption. Metabolites such as L-glutamate were up-regulated in BS. Levels of amino acids and lysophosphatidylcholines were increased in LP. Metabolites such as 4-hydroxyquinoline and 3-formylindole etc. were up-regulated in LB. These results provide a basis for the use of L. parafarraginis and B. subtilis as probiotics in the ecological culture of E. sinensis.