Fate of rapeseed meal polysaccharides during digestion in pigs and poultry : effect of processing and enzyme addition

In this thesis, the fate of non-starch polysaccharides (NSP) from rapeseed meal (RSM) during fermentation in vitro and in vivo was studied. The aim was to understand and improve the fermentation of NSP from RSM in poultry and pigs, by processing and enzyme addition. First, the NSP-structures in RSM were characterized as being branched arabinan, arabinogalactan type II, homogalacturonan, glucurono-xylan, XXGG- and XXXG-type xyloglucan, and cellulose. Second, RSM was processed using shear, heat, and acid prior to in vitro incubation, in the presence or absence of pectolytic enzymes. Acid-treatment combined with pectolytic enzymes was the best option to improve NSP-solubilization in vitro. Unprocessed and acid-extruded RSM with or without addition of enzymes were fed to broilers. In broilers, 22% of the NSP in unprocessed RSM could be fermented, which only significantly improved to 38% by addition of commercial pectolytic enzymes. In broilers’ excreta, XXXG-type xyloglucan, (glucurono-)xylan, arabinan, and cellulose remained unfermented. Unprocessed and acid-extruded RSM was also fed to growing pigs and NSP-fermentation was followed along the digestive tract. In pigs, at the terminal ileum 22% of the NSP was cumulatively fermented and total tract around 70% was fermented. Acid-extrusion improved total tract NSP-fermentability in pigs numerically by 4% points. Water-soluble carbohydrates were nearly completely fermented. In the feces some rhamnogalacturonan, (branched) arabinan, linear xylan, XXXG-type xyloglucan, galactomannan, and cellulose remained. Surprisingly, during alkaline extraction of the broilers’ excreta and pigs’ feces, around 40% (w/w) of the insoluble carbohydrates was released as glucosyl- and/or uronyl-rich carbohydrates, probably originally present via ester-linkages or hydrogen-bonding within the cellulose-lignin network. These linkages are expected to hinder complete NSP-fermentation.