Mannooligosaccharides, also known as mannooligosaccharide and mannooligosaccharide, is a new type of antigenic active substance extracted from the cell wall of yeast culture. It is widely found in konjac powder, melon bean gum, sesbania gum and a variety of microbial cell walls. Because it not only has low heat, stable, safe and non-toxic good physical and chemical properties, but also has the role of protecting the intestinal tract and improving immunity, it has been widely used as a feed additive in feed industry abroad.