Effects of dietary Bacillus cereus, B. subtilis, Paracoccus marcusii, and Lactobacillus plantarum supplementation on the growth, immune response, antioxidant capacity, and intestinal health of juvenile grass carp (Ctenopharyngodon idellus)

•Dietary Bacillus subtilis, Paracoccus marcusii, and Lactobacillus plantarum significantly improved the growth of grass carp.•Dietary B. cereus, B. subtilis, and P. marcusii elevated antioxidant property and decreased permeability of intestine.•B. cereus, B. subtilis, and P. marcusii supplementation suppressed the expression of inflammation-related genes. This study was aimed to evaluate the effects of dietary supplementation of probiotics Bacillus cereus (BC), B. subtilis (BS), Paracoccus marcusii (PM), and Lactobacillus plantarum (LP) on growth, immune response, antioxidant property, and intestine health of juvenile grass carp. Our results showed that dietary probiotics could promote the growth performance, which was significantly increased in BS, PM, and LP groups compared to the fish in Control group. Also, probiotics supplementation significantly enhanced the immunity of fish measured by the content of C3 and C4, and/or AKP activity in serum, and elevated antioxidant property of intestine accompanying by a significantly lower content of malondialdehyde. Compared to Control group, dietary B. cereus and B. subtilis significantly affected intestinal antioxidant system through Nrf2 signaling pathway by up-regulating the expression of catalase, CuZn superoxide dismutase and/or Mn superoxide dismutase, and further improved the intestinal barrier function by up-regulating mRNA levels of ZO-1, ZO-2, ZO-3, and Clauding-12. Besides, B. cereus, P. marcusii, and L. plantarum supplementation could decrease intestinal inflammation by suppressing TLR4 signaling pathway, meanwhile P. marcusii supplementation up-regulated the expression of ZO-2 and ZO-3. Overall, our results indicated that dietary B. cereus, B. subtilis, P. marcusii, and L. plantarum had a positive impact on the growth performance, immunity and antioxidant property of grass carp, and B. cereus, B. subtilis, and P. marcusii exerted benefits on the intestinal health through elevating antioxidant property and decreasing permeability of intestine.