Residual activity of an Escherichia coli-derived phytase and a commercially available Peniophora lycii phytase along the digestive tract of broiler chicks was compared in order to evaluate their relative resistance to hydrolysis in the digestive tract. Seventy-two 7-d-old male broiler chicks were grouped by weight into six blocks of three cages with four birds per cage. Three corn-soybean meal-based diets were randomly assigned to cages within each block. The three diets were a low P diet containing 3.9 g P kg-1 diet; and low P diet plus either E. coli-derived phytase or the P. lycii phytase at 1000 units kg-1 of feed. The chicks were fed experimental diets from 8 to 22 d of age. At the end of the study, chicks were killed and the contents of the crop, proventriculus and gizzard, jejunum and ileum were collected, freeze-dried, ground and analyzed for phytase activity. Escherichia coli-derived phytase had more residual activity at the proventriculus and gizzard, jejunum and ileum when compared with the P. lycii phytase (P < 0.0001). The E. coli-derived phytase may be more resistant to hydrolysis in the digestive tract when compared with the P. lycii phytase.
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Onyango et al. (2005) studied this question.