In swine production, using feed antibiotics as antimicrobial growth promotants has been reduced; thus, feed alternatives to manage gut health are required. Dietary fiber, resistant starch, oligosaccharides, and exopolysaccharides are carbohydrate structures and are nutritional tools that may enhance gut health in pigs. Dietary carbohydrates may have a role to alleviate diarrheal diseases including in pigs post-weaning but also reduce constipation in sows. Antibiotics are hypothesized to influence gut health via modulation of intestinal microbial profiles; fermentation and intestinal inflammation are considered important mechanisms. Dietary fiber sources differ in 2 key properties: fermentability and solubility. Rapid fermentation of fiber and oligosaccharides is associated with changes in microbial profiles and increased metabolite production. Recently, microbial composition was hypothesized to be less important and combined output of metabolites should be the focus. Fiber properties may also manipulate retention time and physico-chemical properties of the undigested residue; hence, non-fermentable insoluble fiber may prevent constipation in sows. Starch is mostly digested and absorbed as glucose. However, resistant starch is not digested and acts as insoluble but fermentable fiber and has unique properties, because it specifically increases intestinal abundance of bifidobacteria, which are associated with improved gut health. Using crop breeding, feed processing, and feed additives, the structure of fiber and starch can be altered thereby changing its degradation kinetics and affecting its utilization as energy source and its prebiotic activity. Finally, exopolysaccharides from Limosilactobacillus reuteri and unique oligosaccharides may serve as receptor analogues for pathogenic bacteria, e.g., enterotoxigenic Escherichia coli (ETEC). These receptor analogues block lectin domains of bacterial adhesins and thus prevent adherence of pathogens to the gut wall, thereby avoiding initiation of post-weaning diarrhea.
In conclusion, dietary carbohydrates are important energy sources but may also provide important solutions to maintain gut health in pigs.