Use of Oligosaccharides in Swine Nutrition
Oligosaccharides typically available for use in swine diets have the common feature that the glycosides are linked via a β bond. This is important since it ensures that the carbohydrate will be available for fermentation by the intestinal microflora. The oligosaccharides differ substantially in their monosaccharide composition and degree of polymerization. The oligosaccharides function as prebiotics. Prebiotics refer to compounds that influence dominant microbial species in the intestinal microbial population. Typically, the prebiotic functions by providing a substrate that allows specific bacterial specie(s) to predominate, and that bacterial specie(s) confers an intestinal health advantage to the animal. The specie-specific function of oligosaccharides makes the monosaccharide composition and degree of polymerization vitally important. The polymer length and monosaccharide composition must be recognizable by the organism that is being selected for propagation in the intestinal tract.
Our research model has been a short chain fructooligosaccharide (scFOS) fed to swine. This compound was selected because it was identified in human and swine milk, was shown to have health benefits in human infants and patients recovering from intestinal anastomosis. The health benefit was believed to occur via the trophic effect of scFOS on the Bifidobacteria population. Bifidobacteria are associated with the intestinal mucosa, are believed to stimulate mucin production by the intestinal epithelia, and synthesize antimicrobial compounds apparently specific against several pathogenic species of bacteria. Our research demonstrated that feeding scFOS increased surface area of the large and small intestine without increasing the proliferative zone of the epithelia. Protein digestion was improved, and growth rate of the pig was also improved. In a pathogenic Escherichia coli experiment, feeding scFOS prevented infection in the neonatal pig. Likewise, in a pathogenic Clostridium difficile experiment feeding scFOS prevented infection in hamsters. We have repeatedly measured a reduction in fecal population of food-born pathogenic bacteria. Feeding scFOS also reduced the concentration of aromatic compounds in the feces, and consequently the malodor associated with excreta. The reduction in skatole could also improve meat quality by reducing the compound primarily associated with boar taint.
The prebiotic effect can occur either by direct effect upon a pathogenic organism or by stimulating growth of beneficial microflora that in turn reduce the growth potential of pathogenic microflora. The first step in evaluating oligosaccharides is to determine the prebiotic mode of action preferred and its specificity. In the scFOS model that we have used, scFOS was selected for its specificity to stimulate growth of Bifidobacteria. Bifidobacteria are unique in that they synthesize β galactosidase, with high specificity for short chain galactosides. Thus, feeding scFOS provides a substrate in the intestinal tract that promotes the growth of Bifidobacteria. Equally important, the scFOS is not well used or not used at all by other bacterial species, especially potential pathogens such as Escherichia coli or Salmonella species. The oligosaccharide should be characterized for its influence upon both the target and nontarget microbial species in the intestinal tract. Specificity of the oligosaccharide will be determined by the monosaccharide composition, degree of polymerization, and spatial arrangement of the oligosaccharide.
Finally, the oligosaccharide should also be characterized for its fermentation characteristic. The species of bacteria selected by the oligosaccharide will influence the end products of fermentation. Increased yields of butyric acid are potentially beneficial, given the effect of butyric acid on growth of intestinal mucosa. The fermentation rate of the oligosaccharide can influence the region of the intestinal tract that increased fermentation occurs. Rapidly fermented oligosaccharides most likely have greater influence in the jejunum, cecum, and proximal colon whereas oligosaccharides with a more moderate fermentation rate would exert their influence more distally. While the research is lacking to support this hypothesis, the greatest benefit might be realized when a diet was formulated to enhance fermentation throughout the fermentative region of the intestinal tract.