Intestinal degradation in pigs of rye dietary fibre with different structural characteristics

Abstract

In order to investigate the effects of dietary fibre (DF) characteristics on carbohydrate degradation and the metabolism in the large intestine, pigs were fed on four rye-bread diets (based on whole rye, pericarp/testa, aleurone or endosperm) with differences in characteristics and amount of DF. The degradability of DF in the large intestine varied greatly between diets. The pericarp/testa DF was hardly degraded in the large intestine, whereas endosperm DF was extensively and rapidly degraded in the caecum. Caecal degradation of aleurone DF was also limited, leaving more material to be degraded in the colon. The undegradable pericarp/testa DF was characterized by high contents of lignin, cellulose, ferulic acids and highly substituted arabinoxylans (the major DF component in rye). Ingestion of this diet resulted in increased faecal bulk and reduced transit time, but with low colonic pH and the lowest concentrations of short-chain fatty acids (SCFA). The aleurone diet, on the other hand, led to a fermentation pattern which may be considered more optimal, with lower colonic pH and higher concentrations of SCFA, in particular butyric acid. Despite the large differences in carbohydrate fermentation only minor significant effects on the presence of protein degradation products and on histological measurements (height and diameter of colonic crypts and thickness of the muscularis externa) were observed.

Processing of rye bran influences both the fermentation of dietary fibre and the bioconversion of lignans by human faecal flora in vitro

“…6 The release of carbohydrates causes a delay in the fermentation process, as shown in this study: a soluble rye bran extract was fermented rapidly and the other substrates containing undegraded cell-wall tissues were fermented slowly. This is in accordance with the results of Glitsø et al 30,31 Xylanase treatment of rye bran made the carbohydrates of cell-wall structures more accessible to colonic microbiota and thus increased the initial rate of fermentation (Fig 2c). Xylanase treatment, however, hydrolysed cell walls only partly, because the consumption of carbohydrates of xylanase-treated rye bran was very similar to that of extruded rye bran.…”

Comparative study of colorectal health related compounds in different types of bread: Analysis of bread samples pre and post digestion in a batch fermentation model of the human intestine

“…Although different types of bread differed substantially in their amounts of dietary fibre compounds (Table 2), no significant differences of faecal bacteria profiles and cell counts in the fermentation solids of bread samples were observed in this study (results not shown), an aspect which was also reported by Gråsten et al (2007) for postmenopausal women after dietary intervention with low-or high-fibre bread. Anyhow, the likely prebiotic properties of bread samples observed in this study were also suggested for different cereals and cereal milling fractions in human intervention trials (Constabile et al, 2008) and animal studies (Canzi et al, 1994;Glitsø, Brunsgaard, Højsgaard, Sandström, & Bach Knudsen, 1998). Vardakou et al (2008) observed that particularly the insoluble wheat arabinoxylans induce xylanase and ferulic acid esterase activities of faecal anaerobes in human intestinal model systems.…”

Molecular weight changes of arabinoxylans of wheat and rye incurred by the digestion processes in the upper gastrointestinal tract of pigs

“…Due to their structural characteristics, dietary fibre (DF) influences digestion and absorption processes along the gastrointestinal (GI) tract (Glitsø et al, 1999). Arabinoxylans, the most important DF of cereals, represent a heterogenic group of polysaccharides of high molecular weight which are comprised of xylan backbones substituted to various degrees with arabinose residues (Fincher and Stone, 1986) according to grain tissues and botanical origins.…”