Cereal non-starch polysaccharide degradation by dietary enzymes in broilers

Chicken feed includes cereals such as wheat, corn and barley, while soy and rapeseed can be added as a protein source. Besides starch, the cereals contain non-starch polysaccharides (NSP) such as cellulose and arabinoxylan. Soy and rapeseed also contain NSP, mainly in the form of pectin, cellulose and xyloglucan. The presence of NSP, especially soluble cereal arabinoxylan, increases the viscosity of the fluid in the gastrointestinal (GI) tract, resulting in reduced nutrient absorption. Supplementation of chicken feed by xylanases has been shown to reduce the viscosity in the GI tract, thereby improving chicken performance. In addition, the enzymatic degradation of NSP leads to the formation of oligosaccharides that are reported to exhibit prebiotic activity and immunomodulatory properties. For instance, xylanase supplementation in wheat-based feeds has been shown to lead to the release of arabinoxylan oligosaccharides (AXOs), which are suggested to act as prebiotics. However, oligosaccharide release is not observed when other cereals, such as maize, are used as feedstock. In the case of maize, the more complex arabinoxylan structure and cell wall architecture hinder enzymatic activity. Still, enzyme supplementation in maize-based diets resulted in improved animal performance. Therefore, it becomes important to investigate in-depth the mechanism by which NSP-degrading enzymes, particularly xylanases, influence animal performance fed wheat and maize-based diets. A previous in vivo trial demonstrated that broiler feed supplementation with Huvepharma enzymes (Hostazym X and Hostazym C) significantly increased the body weight (BW) and mean daily weight gain (ADWG) of broilers from the first days of the trial, which continued to increase during the entire course of the experiment, when compared to the control treatment. Feed conversion rate (FCR) values were lower than the ones of the control feed (no enzyme added) showing a better use of the feed. Such findings demonstrate the beneficial effect of fibre-degrading enzyme supplementation in feed as illustrated by the improved broiler performance. Yet, the underlying mechanism linking enzyme degradation of fibres and improved animal health and performance has not been fully elucidated. It therefore becomes important to characterize the activity of these enzymes, in order to gain insight on the underlying mechanism governing fibre degradation in vivo. Mechanistic insights on the degradation of soluble and insoluble fibres from wheat and maize will be sought. Additionally, this project will attempt to investigate impact of cell wall disruption by fibre-active enzymes on the bio-availability of starch and proteins. Such experiments should also be correlated with in vivo animal trials and in vitro fermentation studies to elucidate the full extent of the beneficial effect of NSP-degrading enzymes supplementation in animal feed.