Xylanases with different substrate affinities in broiler diets

Three xylanase products (Enzymes A, B and C) were examined for their effect on the apparent metabolisable energy (AME), growth rate and digesta characteristics of broilers fed two Australian wheats (Currawong and Harvey). Enzymes increased (P<0.001) weight gain regardless of wheat type. There was an overall increase in AME values of both wheats due to enzyme inclusion. The AME value of the Currawong wheat was not affected by the enzymes, whereas Enzymes A and C markedly (P<0.05) improved the AME value of the lower ME Harvey wheat. Enzyme A reduced (P<0.05) excreta moisture regardless of wheat type. A wheat type x enzyme interaction (P<0.001) on the viscosity of the jejunal and ileal digesta showed different responses of digesta viscosity depending on wheat type. Whilst both Enzymes A and B increased the soluble non-starch polysaccharides (NSP) levels in the small intestine, their effect on digesta viscosity was contrasting. Enzyme A decreased digesta viscosity (P<0.05), but Enzyme B elevated (P<0.05) it. These responses were most noticeable with the lower ME wheat. Enzyme C had no effect on the soluble NSP levels, but significantly (P<0.05) reduced viscosity in the small intestine.