The role of functional properties of dietary fiber in the control of nutrient flow and intestinal health in pigs

Abstract

Viscosity and fermentability are considered important properties of dietary fiber. Viscosity increases digesta viscosity and reduces digesta passage rate, nutrient digestion and absorption whereas fermentability increases fermentation into short chain fatty acids (SCFA). The objectives were to enhance the understanding of these properties of dietary fiber and their effects on digestive physiology using surgical models in pigs. In study 1, three catheterized pigs fed 3 diets containing 0, 3, or 6% oat β-glucan concentrate (BG0, BG3, and BG6) in a repeated 3 × 3 Latin square. Pigs fed BG6 had a lower net glucose flux. Pigs fed BG6 tended to have lower portal C-peptide without lowered insulin. Pigs fed BG6 had lower portal glucose dependent insulinotropic peptide (GIP) and glucagon like peptide-1 (GLP-1), which in turn were correlated (R2 = 0.81 and 0.88, respectively) with portal glucose. Pigs fed BG3 and BG6 had a higher net SCFA flux, indicating increased fermentation. In study 2 and 3, ileal cannulated grower pigs were fed semi-purified diets supplemented with 5% purified non-starch polysaccharides (NSP) in a 2 (low and high viscous) × 2 (low, and high fermentable) factorial arrangement using cellulose (CEL), carboxymethylcellulose (CMC), and low and high viscous oat β-glucan (LBG and HBG, respectively). The CMC, LBG and HBG induced high ileal digesta viscosity coinciding with high nutrient digestibility; in contrast, CEL had lowest viscosity and nutrient digestibility. The CEL, LBG and HBG increased fecal SCFA. Linear discriminate analysis of NSP and TRFLP profiles and 16S rRNA gene copy numbers of bacterial groups revealed that CMC resulted in distinctive bacterial communities. The gene copy number of butyryl-CoA CoA transferase was higher than for butyrate kinase, indicating that this pathway is dominant for butyrate production in pigs. In study 4, similar dietary treatments were fed to catheterized pigs. High viscous and fermentable HBG increased net butyrate flux and insulin and GLP-1 production but did not affect net glucose flux. Thus, the viscosity and fermentability are important functional properties of dietary fiber that better explained the physiological effects on kinetics of digestion, absorption, hormones responses, fermentation and thus nutrient flow and intestinal health.