Fig. 3

Overview of the possible functions of milk carbohydrates on the intestine of nursery pigs. Lactose and various type of milk oligosaccharides could improve the intestinal maturation and health of nursery pigs through positively modulating enterocyte proliferation, intestinal immune response, and microbiota. (1) Lactose would be hydrolyzed by lactase producing galactose and lactose, which are utilized to produce energy for the growth and maintenance of nursery pigs. (2) lactose at optimal level could induce a favorable condition against pathogenic bacteria by microbial fermentation of saccharolytic bacterial groups, including Lactobacillus and Bifidobacterium, leading to preventing pathogen colonization in the intestine of nursery pigs. In addition, (3) milk oligosaccharides could modulate the growth of intestinal epithelium through binding to toll-like receptors (TLRs) and epidermal growth factor receptors (EGFR) on the enterocytes. (4) Milk oligosaccharides can increase gene expression of mucus secretion and prevent the pathogen from binding to intestinal immune-related receptors including TLRs and various types of glycan receptors, leading to enhanced mucosal immune homeostasis and tolerance. (5) Milk oligosaccharides can prevent pathogen colonization by increased abundance of Bifidobacterium and production of lactic acid and volatile fatty acids (VFA)