Simultaneous application of phytase and xylanase to broiler feeds based on wheat: in vitro measurements of phosphorus and pentose release from wheats and wheat-based feeds†

An in vitro procedure that simulated digestion in growing broilers was tested to predict phosphorus availability and arabinoxylan hydrolysis in samples of nine wheat varieties and in a wheat-based diet. Amounts of dialysable phosphorus freed from wheat samples correlated with activities of endogenous phytase (R = 0.913; p < 0.0001), whereas amounts of pentoses released were correlated with viscosities of the digested samples (R = 0.899; p < 0.0001). Differences in phosphorus release resulting from graded levels of microbial phytase added to feeds that were either autoclaved or not autoclaved revealed a decreasing role of endogenous phytase in dephosphorylation as levels of microbial phytase supplementation grew. Amounts of pentoses released from feeds containing two different xylanase preparations reflected literature data on different in vivo efficacies of those preparations. Simultaneous addition of phytase and xylanase affected phosphorus release in a manner that depended upon the form of xylanase preparation used (liquid or powder). There was a positive influence of acid protease on both phytate and arabinoxylan hydrolysis in feeds supplemented with phytase. Effects observed by the in vitro procedures corresponded to in vivo phenomena described in the literature. © 1999 Society of Chemical Industry