Temperature Resistance of Xylanase Inhibitors and the Presence of Grain-Associated Xylanases Affect the Activity of Exogenous Xylanases Added to Pelleted Wheat-Based Feeds

The addition of exogenous xylanases (EX-XYL) to wheat-based poultry feeds is a common practice today. Wheat contains xylanase inhibitors (XI) and grain-associated xylanases (GA-XYL), which could affect the action of the EX-XYL. In this study, both GA-XYL and XI activity in feeding-quality wheat were assessed. In addition, the effect of the conditions during digestion in monogastrics and the effects of pelleting at different conditioning temperatures on GA-XYL and XI were investigated. The GA-XYL activity varied between no activity and 0.821 XU/g. In contrast, the XI activity was consistently high in all wheat samples and ranged between 259 and 331 IU/g. Simulating the digestive process did not affect the activities of GA-XYL or XI. Pelleting at 85 degrees C or higher reduced the XI activity up to 46%. GA-XYL, however, were more heat-sensitive, and their activity was reduced to 67% at 60 degrees C. The extract viscosity increased and the release of reducing sugars decreased at higher conditioning temperatures. In addition, the net effect of EX-XYL on extract viscosity increased at higher temperatures, whereas the release of reducing sugars was not affected. In conclusion, XI affected the action of EX-XYL during the digestive process, and pelleting did not eliminate their negative effects.