Clostridium butyricum metabolites mitigate inflammatory responses in Ctenopharyngodon idella post-overwintering and enhance resistance to Aeromonas hydrophila.

Abstract

Clostridium butyricum metabolites (CBM) serve as a functional supplement with anti-oxidant and immune-enhancing properties, yet its role in aquatic animals subjected to dietary high plant-derived diets and over-wintering remain understood. The present study evaluated the effect of CBM on anti-oxidative capacities and immunity in grass carp post-overwintering and its resistance of pathogen challenge. Based on our previous investigations, grass carp were fed three diets over 60 days, low cottonseed and rapeseed meal diet (CON), high cottonseed and rapeseed meal diet (CBM0) and CBM-supplemented diet (CBM1), respectively, followed by 4-month overwintering treatment. The findings demonstrated that CBM supplementation maintained liver and gut health of grass carp as evidenced by reduced serum D-lactate level, transaminase activities, decreased hepatocyte vacuolization (P&#xa0;<&#xa0;0.05). Moreover, liver and intestinal antioxidant properties were enhanced by supplementation with CBM, as demonstrated by the decrease in malondialdehyde content (P&#xa0;<&#xa0;0.05), and enhancement in superoxide dismutase, catalase, and glutathione peroxidase levels, and up-regulation of mnsod, cat, gsto, and gpx1 levels. Supplementation of CBM suppressed p38mapk, tlr2, myd88, nfkb, and tnf-&#x3b1;, coupled with the increased complement C4, immunoglobulin M, and tgf-&#x3b2;1 and il-15 levels (P&#xa0;<&#xa0;0.05). Moreover, under Aeromonas hydrophila infection, grass carp ingesting CBM showed markedly decreased mortality compared to CBM0 (P&#xa0;<&#xa0;0.05). This research demonstrated that overwintering stress markedly increased the incidence of oxidative stress and inflammatory responses in grass carp. CBM can alleviate overwintering inflammation and oxidative damage, and enhance antibacterial capacity.