Regulating Effect Of Mannan Oligosaccharides On The Adhesive Quantity Of Gut Mucus And The Expression Of Immune-related Gene In Grass Carp (Ctenopharyngodon Idellus)

This study was conducted on grass carp (Ctenopharyngodon idellus) to study the effect of mannan oligosaccharides (MOS) on the adhesive quantity of gut mucus and the expression of immune-related gene.1. In the experiment of study on the effects of mannan oligosaccharides on the adhesive quantity of gut mucus, the same size and weight grass carp were randomly divided into two groups:the control (CON) group was fed with basal diet, and the treatment (MOS) group was fed with basal diet supplemented with0.2%mannan oligosaccharides. The fish were fed their respective diets for48d. The gut mucus was isolated from the grass carp after feeding. The certain concentration of mucin was fixed and incubate with bacteria. Gram stain was done when adhesive bacteria fixed, the number of bacteria was counted by the oil microscope. The effect of dietary mannan oligosaccharide on the adhesion ability of Aeromonas hydrophila, Escherichia coli, Lactobacillus coli and Bacillus subtilis to intestinal mucus of grass carp. The result showed that mannan oligosaccharides improve the adhesive quantity of Aeromonas hydrophila and Bacillus subtilis significantly (P<0.05) besides Escherichia coli and Lactobacillus coli. The results suggested that mannan oligosaccharides increase the adhesion of Bacillus subtilis and Aeromonas hydrophila to the intestinal mucus of grass carp.2. The aim of the study was to investigate the effect of mannan oligosaccharides added in feeds on immune-related gene expression profile in grass carp experimentally infected with Aeromonas hydrophila (Ah). After feeding grass carp with Bio-MOS(?)(MOS) and control (CON) diets for28days. Head-kidney, liver and spleen were collected from infected (n=4) and non-infected (n=4) fish on hours48h,72h and96h. Hindgut were collected from infected (n=4) and non-infected (n=4) fish on hours24h,48h,72h,96h and120h. Gene expression of IL-1β and IL-10in head-kidney, liver and spleen and gene expression of IL-1β, IL-10, IFN and TLR4in hindgut were investigated by real-time PCR. Our result showed mannan oligosaccharides modulate the cytokines in innate immunity of grass carp, regulation varid in different tissuse after injection. In head-kidney, gene expression of IL-1β in MOS/I (feed containing0.2%Bio-MOS(?)+injection with Ah) group was significantly higher than CON/I (non-supplemented feed+injection with Ah) group at48h; gene expression of IL-10in MOS/I group was significantly higher than CON/I group at72h and was significantly lower than CON/I group at96h. In spleen, gene expression of IL-1β in MOS/I group was significantly lower than CON/I group at72h and96h; gene expression of IL-10in MOS/I group was significantly lower than CON/I group at48h and96h. In liver, gene expression of IL-1β and IL-10in MOS/I group were significantly higher than CON/I group at48h, but lower than CON/I group at72h and96h. In hindgut, gene expression of IL-1β in CON/I group was significantly higher than MOS/I group at24h, gene expression of IL-1β in CON/I group increased at48h,72h and96h. IL-1β gene in MOS/I group expressed smoothly. Gene expression of IL-10in MOS/I group was higher at the beginning of infection, but decrease after72h. Gene expression of IFN in MOS/I group was significantly higher than CON/I group at most of time points (expect72h). Gene expression of TLR4in MOS/I group was significantly higher than CON/I group at48h and72h. These findings demonstrated that mannan oligosaccharides induce host stimulatory responses which ultimately enhance disease resistance when pathogenic bacteria intruding.