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 -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 -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. / Animal Science

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Thesis (Ph. D.)--University of Washington, 1991. / Vita. Includes bibliographical references (leaves [129]-137).

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

The primary objective of this study was to investigate the effect of dietary fiber on methanogenic diversity and community composition in the hindgut of indigenous Chinese Lantang gilts to explain the unexpected findings reported earlier that Lantang gilts fed low-fiber diet (LFD) produced more methane than those fed high-fiber diet (HFD). In total, 12 Lantang gilts (58.7±0.37 kg) were randomly divided into two dietary groups (six replicates (pigs) per group) and fed either LFD (NDF=201.46 g/kg) or HFD (NDF=329.70 g/kg). Wheat bran was the main source of fiber for the LFD, whereas ground rice hull (mixture of rice hull and rice bran) was used for the HFD. Results showed that the methanogens in the hindgut of Lantang gilts belonged to four known species ( Methanobrevibacter ruminantium, Methanobrevibacter wolinii , Methanosphaera stadtmanae and Methanobrevibacter smithii ), with about 89% of the methanogens belonging to the genus Methanobrevibacter . The 16S ribosomal RNA (rRNA) gene copies of Methanobrevibacter were more than three times higher ( P <0.05) for gilts fed LFD (3.31×10 9 copies/g dry matter (DM)) than gilts fed HFD (1.02×10 9 copies/g DM). No difference ( P >0.05) was observed in 16S rRNA gene copies of Fibrobacter succinogenes between the two dietary groups, and 18S rRNA gene copies of anaerobic fungi in gilts fed LFD were lower than ( P <0.05) those fed HFD. To better explain the effect of different fiber source on the methanogen community, a follow-up in vitro fermentation using a factorial design comprised of two inocula (prepared from hindgut content of gilts fed two diets differing in their dietary fiber)×four substrates (LFD, HFD, wheat bran, ground rice hull) was conducted. Results of the in vitro fermentation confirmed that the predominant methanogens belonged to the genus of Methanobrevibacter , and about 23% methanogens was found to be distantly related (90%) to Thermogymnomonas acidicola. In vitro fermentation also seems to suggest that fiber source did change the methanogens community. Although the density of Methanobrevibacter species was positively correlated with CH 4 production in both in vivo ( P <0.01, r =0.737) and in vitro trials ( P <0.05, r =0.854), which could partly explain the higher methane production from gilts fed LFD compared with those in the HFD group. Further investigation is needed to explain how the rice hull affected the methanogens and inhibited CH 4 emission from gilts fed HFD.

The aim of this study was to understand the cellular mechanisms in enterocytes, which may decrease glucose uptake by viscous oat β-glucan. An in-vitro cell model examined the effect of diffusion limitation, fluid shear stimulation, and increased intestinal stretching. Mechanical stimulation of IEC-6 was assessed. A Flexcell Cell Streamer device applied different fluid flow stresses on cells. Flexcell FX-4000 was used for biaxial stretching of the cells. Following the confirmation of appropriate use of the cell model, the results indicated that high viscosity oat β-glucan might provide a physical barrier limiting diffusion of nutrients to the cells apical surfaces. Western blot analysis confirmed weak mechanical stimulation on the cells. Mechanical stimulation did not influence glucose uptake. Strain-induced cells showed lower activities in their glucose uptake. In conclusion, there may be a significant contribution of direct effects of the viscosity of oat β-glucan on cellular mechanisms of uptake in enterocytes.

Thesis (Ph. D.)--University of Washington, 1987. / Vita. Bibliography: leaves [116]-129.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 77-90).

Thesis (M.Sc. (Food and Nutrition for Development))--Mahidol University, 2007. / LICL has E-Thesis 0030 ; please contact computer services.