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

An in vitro procedure that simulated digestion in growing broilers was test ed to predict phosphorus availability and arabinoxylan hydrolysis in sample s of nine wheat varieties and in a wheat-based diet. Amounts of dialysable phosphorus freed from wheat samples correlated with activities of endogenou s phytase (R = 0.913; p < 0.0001), whereas amounts of pentoses released wer e correlated with viscosities of the digested samples (R = 0.899; p < 0.000 1). Differences in phosphorus release resulting from graded levels of micro bial phytase added to feeds that were either autoclaved or not autoclaved r evealed a decreasing role of endogenous phytase in dephosphorylation as lev els of microbial phytase supplementation grew. Amounts of pentoses released from feeds containing two different xylanase preparations reflected litera ture data on different in vivo efficacies of those preparations. Simultaneo us 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 arab inoxylan hydrolysis in feeds supplemented with phytase. Effects observed by the in vitro procedures corresponded to in vivo phenomena described in the literature. (C) 1999 Society of Chemical Industry.