Viscosity is a physicochemical property associated with dietary fibers, particularly soluble dietary fibers. Viscous dietary fibers thicken when mixed with fluids and include polysaccharides such as gums, pectins, psyllium, and β-glucans. Although insoluble fiber particles may affect viscosity measurement, viscosity is not an issue regards insoluble dietary fibers. Viscous fibers have been credited for beneficial physiological responses in human, animal, and animal-alternative in vitro models. The following article provides a review of viscosity as related to dietary fiber including definitions and instrumentation, factors affecting viscosity of solutions, and effects of viscous polysaccharides on glycemic response, blood lipid attenuation, intestinal enzymatic activity, digestibility, and laxation.

Viscosity as Related to Dietary Fiber: A Review

Many feed ingredients in use in monogastric diets contain significant quantities of antinutritional factors (ANF) which limit both their feed value and their use. Almost all enzymes currently being used address such factors to varying degrees, allowing for more economic utilization of raw materials. However, animal response to xylanase, beta-glucanase and even phytase utilization reported in the literature tends to vary. Factors such as enzyme source, ingredient variety and environment under which the ingredient was grown, stored and processed into animal feed, age of animal, interaction with other dietary ingredients, and health status are shown to affect significantly the response obtained. As a result, the mode of action of xylanases and beta-glucanases is still debated due to too much emphasis being placed on interpretation of individual trial results without regard to the interactive factors or the literature dataset as a whole. Better understanding of such factors will improve data interpretation. While results with phytase are not subject to such extreme variation, they are nevertheless inconsistent in the degree to which inorganic phosphorus can be replaced by this enzyme. Greater understanding of the ANF and factors which interact to govern the response to added exogenous enzymes will undoubtedly improve the economic return and confidence in their use. Improved knowledge of ANF structure will result in development of enzymes directed towards far more specific targets, which enhances the likelihood of success and should reduce the overall enzyme usage.

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Exogenous enzymes for pigs and poultry

1 The mechanism of the anti-nutritive activity of isolated wheat pentosans was investigated by examining the roles of digesta viscosity and gut microflora in broiler chickens 2 Wheat pentosans were isolated by alkaline extraction and purified by sequential treatment with pancreatin, alpha-amylase and lichenase, and high-speed centrifugation Some of the pentosans were depolymerised using a beta-xylanase, which reduced the relative viscosity of the polysaccharides 4 fold 3 Inclusion of 35 g alkali-extractable pentosans (containing 854 g arabinoxylans/kg DM) per kg diet significantly (P less than 005) depressed broiler performance and the viscosity of the digesta of these birds was significantly (P less than 005) higher than that of controls Addition of the same amount of depolymerised pentosans had no significant effect on bird performance and had less effect on digesta viscosity 4 Supplementation of the diet containing wheat pentosans (30 g/kg) with procaine penicillin (150 mg/kg) did not improve bird performance 4 It is concluded that the wheat pentosans elicit their anti-nutritive activity predominantly through increasing the viscosity of digesta

Anti‐nutritive effect of wheat pentosans in broiler chickens: Roles of viscosity and gut microflora

The physicochemical properties of non-starch polysaccharides (NSPs) are responsible for their antinutritive activities in the broiler chicken. In particular, soluble viscous NSPs depress the digest...

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/19377DD7FDD03D2E61DBFB2186448DBE/S0043933996000207a.pdf/div-class-title-non-starch-plant-polysaccharides-in-broiler-nutrition-towards-a-physiologically-valid-approach-to-their-determination-div.pdf

Non-starch plant polysaccharides in broiler nutrition - towards a physiologically valid approach to their determination

Two pentosan-rich fractions (water-extractable, WEP, and alkali-extractable, AEP) were isolated from a wheat milling by-product. When both WEP and AEP were added to a commercial-type broiler diet the apparent metabolizable energy (AME), nitrogen retention, feed utilization and growth of broilers were significantly (P less than 0.001) depressed. These depressions were closely correlated (P less than 0.001) to the level of pentosans in the diets. At the highest level of inclusion of pentosans (equivalent to 40 g arabinoxylans as AEP/kg) the ileal digestibilities of starch, protein and lipid were decreased by 14.6, 18.7 and 25.8% respectively.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/1F3CC2BF453D80E02C900EDEF9E472A1/S0007114592000151a.pdf/div-class-title-the-inhibition-of-nutrient-digestion-by-wheat-pentosans-div.pdf

Wayne B. White

Papers

Viscosity of β-D-Glucan as a Factor in the Enzymatic Improvement of Barley for Chicks

The Viscosity Interaction of Barley Beta-Glucan with Trichoderma viride Cellulase in the Chick Intestine

An Instrument Suitable for Viscosity Determination of Chick Intestinal Fluids