Variation in levels of non-starch polysaccharides and endogenous endo-1,4-β-xylanases affect the nutritive value of wheat for poultry.

1. Endo-1,4--xylanase is known to improve the nutritive value of wheat-based diets for poultry by degrading dietary arabinoxylans. However, broilers' response to supplementation of wheat-based diets with exogenous endo-1,4--xylanase is not always observed.2. In this study, 108 different wheat lots were analysed for levels of extract viscosity as well as for endogenous endo-1,4--xylanase activity, and the impact of these two variables in animal performance was tested.3. Results revealed that endogenous endo-1,4--xylanase activity and extract viscosity content varied widely among different wheat lots. Thus, a trial was conducted to evaluate the efficacy of exogenous enzyme supplementation in broiler diets using wheats with different levels of extract viscosity and endogenous endo-1,4--xylanase activity.4. The data revealed that exogenous enzyme supplementation was only effective when the wheat present in the diet had high levels of extract viscosity (14.8 cP) with low endogenous endo-1,4--xylanase activity (347.0U/kg). Nevertheless, it is apparent that exogenous microbial xylanases reduce digesta extract viscosity and feed conversion ratio independently of the endogenous properties presented by different wheat lots.5. The data suggest that extract viscosity and/or endogenous endo-1,4--xylanase activity affect the response to enzyme supplementation by poultry fed on wheat-based diets.