Efficacy of Phytase Enzymes for Releasing Phytate-Bound Phosphorus: Effects of Phytase Source, Phytase Level, and Pharmacologic Zinc Supplementation

Previous reviews have covered our work on the efficacy of a new E. coli-derived phytase (expressed in yeast) for releasing phytate-bound phosphorus (P) present in corn-soybean meal diets for young pigs, growing-finishing pigs, broiler chicks and laying hens (Baker and Augspurger, 2002; Augspurger, 2003; Augspurger et al., 2003a). It is not our intent to repeat this information, but instead to present new information. Through characterizing the P-releasing efficacy of a new E. coli-derived phytase, i.e., EcoPhos (ECP), our laboratory showed that the efficacy of two commercially-available fungal phytases, i.e., Natuphos (FP1) and Ronozyme (FP2), were unexpectedly low in the chick, but were higher in the young pig (Augspurger et al., 2003a). These were not the first data to show low efficacy for the fungal phytases in chicks, as Angel et al. (2001) also showed low efficacy values for FP1 in chicks. Recent work by Shirley and Edwards (2003), however, showed that supplementation of FP1 at a level of 12,000 FTU/kg resulted in almost complete digestion and release of the dietary phytate-P, which shows that FP1, at a high level, is capable of hydrolyzing phytate-P almost completely. Thus, our first objective in the work reported herein was to evaluate high levels of ECP, FP1, and FP2 in broiler chicks