K. E. Bach Knudsen

Gastrointestinal implications in pigs of wheat and oat fractions: 1. Digestibility and bulking properties of polysaccharides and other major constituents

The present work was undertaken to study the gastrointestinal effects of wheat and oat dietary fibre (DF) using 40-50 kg pigs cannulated in the terminal ileum. The variables studied were: chemical characteristics of the DF, ileal and faecal digestibility of nutrients and bulking properties of polysaccharides and other major constituents. The wheat products studied included refined wheat flour and wheat fractions rich in the following botanical components: aleurone, pericarp/testa and bran. The oat products used were rolled oats and oat bran. The products varied considerably in DF content (g/kg dry matter) and composition; non-starch polysaccharides (NSP) and Klason lignin content ranged from 34 and 1 g/kg respectively in wheat flour, to 465 and 92 g/kg in pericarp/testa. The main NSPs in the wheat were arabinoxylans (AX) (64-69%) and cellulose (15-31%) and in oats mixed linked beta(1----3; 1----4-D-glucans (beta-glucans; 46-63%) and AX (28-32%). The lowest content of soluble NSP was found in the lignified wheat fractions (bran and pericarp/testa) and the highest in oat bran. Eight diets were produced using the wheat and oat products and studied in two series of experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets prepared by adding DF from the fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series also included diets based on rolled oats and rolled oats plus oat bran. Starch was almost completely digested in the small intestine (0.97-1.00). However, there was a tendency to a slightly lower digestibility of oat starch compared with wheat starch. The recovery of wheat NSP in ileal digesta was 82-104% compared with 64-66% for oats. The low recovery of NSP in oat diets was primarily due to the low recovery of beta-glucans (25-36%). In the large intestine NSP and starch residues were extensively degraded. For the DF-depleted control diets or diets based on oats, 8-17% NSP survived breakdown while in the diets enriched with aleurone, pericarp/testa or bran fractions, NSP recovery was 33, 50 and 38% respectively. Fermentative breakdown of carbohydrates in the large intestine was estimated to contribute between 10 and 24% of the energy for maintenance. Energy derived from the inflow of organic acids from the ileum contributed an additional 1-4% of maintenance energy.(ABSTRACT TRUNCATED AT 400 WORDS)

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

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 shortchain 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 external) were observed.

Effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile and inflammation markers in metabolic syndrome – a randomized study (SYSDIET)

Different healthy food patterns may modify cardiometabolic risk. We investigated the effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile, blood pressure and inflammatory markers in people with metabolic syndrome.

Nutritive value of danish-grown barley varieties, I, carbohydrates and other major constituents

The reproducibility of analytical methods for low molecular weight sugars, starch, soluble- and insoluble dietary fibre (1317), non-starch polysaccharides (NSP) and Klason lignin was tested in an investigation comprising 50 barley samples. The carbohydrate methods were highly reproducible with coefficients of variation varying from 0·6 to 3·9 %. These samples were further analysed for soluble- and insoluble βglucans. The materials used in this investigation included four spring feeding, three spring malting and two winter feeding barley varieties, grown in three different years on a good quality clay soil and a poor quality sandy soil in Denmark. Starch content (% of dry matter) was 1·7 % higher and DF was 2·1 % lower in spring malting than in spring feeding varieties. The lower DF was accounted for by differences in both soluble and insoluble DF. In spring malting varieties, total β-glucan was 4·1% compared to 4·6 and 4·3 % in spring and winter feeding varieties, respectively. The soluble β-glucan fraction was, however, reduced relatively more than the insoluble fraction in malting varieties. The starch, DF and protein contents were strongly affected by both year and locality. For barley varieties grown on the poor quality sandy soil, starch content decreased from 60·3 % in 1981 to 53·8 % in 1983, while DF and protein content increased from 21·5 and 11·4% to 24·4 and 13·5 %, respectively. The strongest effect of year and locality was identified in the spring varieties.

The digestibility of carbohydrates, protein and fat in the small and large intestine of piglets fed non-supplemented and enzyme supplemented diets

The digestibility of carbohydrates, protein and fat was studied in 8- to 12-week-old piglets fitted with a T-shaped cannula at the terminal ileum and fed two diets based on barley and wheat as the cereal source and with protein from soybean meal (diet CS) or pea, soybean meal and rapeseed cake (diet CPSR). The diets were fed either alone or supplemented with single enzymes (α-galactosidase, xylanase, β-glucanase, α-amylase, protease) or with a mixture of enzymes (α-galactosidase, xylanase and protease). After completing the digestibility trials, four piglets on each of the two basal diets were slaughtered and samples of digesta were taken along the gastrointestinal (GI) tract for additional measurements of carbohydrates and organic acids. Three hours after the meal the disappearance of raffinose oligosaccharides (raffinose, stachyose and verbascose) was about 39% as measured in the pooled digesta from the stomach and the small intestine. Digestibility of raffinose oligosaccharides at the terminal ileum was 86–90%. The relatively high digestibility in the upper intestine is most likely caused by endogenous plant and microbial α-galactosidases. The digestibility of starch at all sampling points along the GI tract was significantly higher with diet CS than with diet CPSR, while the digestibility of protein, fat and non-starch polysaccharides was similar for the two diets. In the large intestine, pectin was more rapidly and extensively digested than cellulose, arabinoxylans and xylan polysaccharides but the fermentation yielded similar proportions of acetate, propionate and butyrate. The supplementation of diet CS with xylanase or diet CPSR with the enzyme mixture, increased the digestibility of xylose of diet CS and xylose, arabinose and mannose and DM of diet CPSR. None of the other enzymes, however, improved the digestibility of nutrients.

Gastrointestinal implications in the rat of wheat bran, oat bran and pea fibre

The gastrointestinal (GI) effects of three different dietary fibre (DF) sources: wheat bran (WB), oat bran (OB) and pea fibre (PF), were compared with a low-fibre diet in a 4-week trial with rats (initial bodyweight 210 g). The DF sources varied widely in chemical composition, solubility and water-holding properties, and particle size. The DF sources were mixed into diets to comprise the same amount of non-starch polysaccharides (NSP; 135 g/kg dry matter (DM)). Compared with the control diet, all fibre-containing diets reduced apparent digestibility of DM, energy, and protein significantly but to different extents. The ranking order of faecal DM bulking followed that of NSP recovery in the faeces: WB > OB > PF > control. The elongating effect of the diets on the GI tract was most pronounced in the rats fed on the OB diet. The mean transit time (MTT) of the OB diet was similar to that of the control diet (approximately 37 h), which was significantly slower than the MTT of the WB and PF diets (approximately 23 h). The study confirms that no simple cause and effect relationship exists between chemical composition, physical properties, and physiological effects of dietary fibre and their effects along the GI tract.

Intestinal metabolism of rye lignans in pigs

To study the intestinal metabolism of lignans, the concentrations of plant and mammalian lignans in intestinal digesta sampled along the intestinal tract of pigs were determined by isotope dilution GC-MS. The pigs were fed rye-bread diets made from either whole rye-grains or rye-grain milling fractions enriched in pericarp-testa, aleurone or endosperm cells. The content and characteristics of dietary fibre varied between diets and had been shown to induce different colon fermentation patterns. As the metabolism of lignans depends on the action of the intestinal flora, we tested whether the rye-bread diets influence the metabolism of lignans. In the ileum, the lignans were mainly present as conjugated plant lignans, which were determined only when the analytical procedure included a hydrolysis step. High recovery of dietary lignans in the ileum may indicate that the lignans enter the enterohepatic circulation. In addition, two to three times the intake of lignans were recovered in the faeces when the diets had a high content of dietary fibre suggesting underestimation of plant lignans in the diet. Most of the plant lignans disappeared from the intestinal tract between the terminal ileum and the caecum. The intestinal concentrations and the disappearance of lignans correlated with the content of lignans in the diet, being highest on the pericarp-testa diet and lowest on the endosperm diet. No effect of fermentation pattern on the intestinal metabolism of lignans was observed. The lignans were liberated from the pericarp-testa diet although the plant cell walls remained largely undegraded.

Degradation of rye arabinoxylans in the large intestine of pigs

Four types of rye bread (based on whole rye, pericarp/testa, aleurone or endosperm) differing in arabinoxylan (AX) structure were fed to pigs. Collected intestinal material was extracted with cold water and 4 M potassium hydroxide, and the AX were characterised by methylation analyses. The endosperm AX were extensively and readily degraded in the caecum (0.78), whereas pericarp/testa AX were undegraded in the intestinal tract of pigs. Aleurone AX were also degraded to a large extent (faecal digestibility 0.73) but at a slower rate, and, in agreement, structural modification of aleurone AX also took place beyond the proximal colon. The differences in AX degradability correlated well with differences in water and alkali extractability and differences in structural characteristics of the AX. Endosperm AX were thus characterised by a large content of water-extractable AX and pericarp/testa AX by a very high degree of (mono- and double-) xylose substitution. In contrast, aleurone AX were characterised by the presence of an alkali-extractable AX with a very low degree of substitution, which precipitated upon dialysis of the alkali extract. The faecal xylose substitution patterns were similar irrespective of diet. The study thus showed that the structural characteristics of a dietary fibre component influenced dietary fibre degradation in pigs, which may hold important implications for the colonic health in monogastrics.

Digestion of carbohydrates and utilization of energy in sows fed diets with contrasting levels and physicochemical properties of dietary fiber.

Three experimental diets were used to investigate the digestion of carbohydrates and utilization of energy in sows fed diets with different levels and physicochemical properties of dietary fiber (DF). The low-fiber diet (LF; DF, 16%; soluble DF, 4.8%) was based on wheat and barley. The high-fiber 1 diet (HF1; DF, 41%; soluble DF, 11%) was based on wheat and barley supplemented with the coproducts: sugar beet pulp, potato pulp, and pectin residue, and the high-fiber 2 diet (HF2; DF, 44%; soluble DF, 7.3%) was based on wheat and barley supplemented with approximately 1/3 of the coproducts used in diet HF1 and 2/3 of brewers spent grain, seed residue, and pea hull (1:1:1, respectively). The diets were studied in 2 series of experiments. In Exp. 1, the digestibility and ileal and fecal flow of nutrients were studied in 6 ileal-cannulated sows placed in metabolic cages designed as a repeated 3 x 3 Latin square design. In Exp. 2, energy metabolism was measured in respiration chambers using 6 sows in a repeated 3 x 3 Latin square design. The DF level influenced the ileal flow of most nutrients, in particular carbohydrates, which increased from 190 g/d when feeding the LF diet to 538 to 539 g/d when feeding the HF diets; this was also reflected in the digestibility of OM and carbohydrates (P < 0.05). The ranking of total excretion of fecal materials was HF2 > > HF1 > LF, which also was reflected in the digestibility of OM, protein, and carbohydrates. Feeding HF diets resulted in greater CH(4) production, which was related to the amount of carbohydrates (r = 0.79) and OM (r = 0.72) fermented in the large intestine, but with no difference in heat production (12.2 to 13.1 MJ/kg of DM). Retained energy (MJ/kg of DM) was decreased when feeding HF1 compared with LF and negative when feeding HF2. Feeding sows HF1 reduced the activity of animals (5.1 h/24 h) compared with LF (6.1 h/24 h; P = 0.045).

Absorption of carbohydrate-derived nutrients in sows as influenced by types and contents of dietary fiber.

The current investigation was undertaken to study the absorption and plasma concentration of carbohydrate-derived nutrients [glucose, short-chain fatty acids (SCFA), and lactate] and the apparent insulin production in sows fed diets containing contrasting types and contents of dietary fiber. Six sows were fed 3 experimental diets, low fiber (LF; 177 g of dietary fiber and 44 g of soluble fiber/kg of DM), high soluble fiber (HF-S; 429 g of dietary fiber and 111 g of soluble fiber/kg of DM), and high insoluble fiber (HF-I; 455 g of dietary fiber and 74 g of soluble fiber/kg of DM), in a repeated crossover design. Variations in dietary concentration and solubility of dietary fiber were obtained by substituting starch-rich wheat and barley in the LF diet with dietary fiber-rich co-products (sugar beet pulp, potato pulp, pectin residue, brewers spent grain, pea hulls, and seed residue, which have distinct physicochemical properties). The main carbohydrate component of the LF diet was starch and nonstarch polysaccharides (cellulose and noncellulosic polysaccharides) for the 2 high dietary fiber diets. Consumption of the LF diet resulted in increased and rapid glucose absorption at 0 to 4 h postfeeding. With the HF-I diet, the glucose absorption pattern was similar but at a decreased rate, whereas it was decreased and delayed with the HF-S diet (diet, P < 0.001; time, P < 0.001). These differences were also reflected in the insulin response. The quantitative absorption of SCFA at 0 to 10 h postfeeding was greater when feeding the HF-S diet compared with the LF diet (P < 0.001) and intermediate when feeding the HF-I diet (P < 0.001). The study showed that feeding the high dietary fiber diets resulted in a increased and more uniform uptake of SCFA than when feeding the LF control. Moreover, the HF-S diet reduced diurnal variation in glucose and insulin concentrations.