Phytase improves dietary calcium utilization in chicks, and oyster shell, carbonate, citrate, and citrate-malate forms of calcium are equally bioavailable

Three chick experiments were done to investigate the effect of an Escherichia coli-derived phytase (EcoPhos; Phytex, Portland, ME) and Ca source on the bioavailability of Ca from com-soybean meal diets. Five replicates of four male crossbred chicks were fed experimental diets from day 8 to day 18 or 20 posthatch. In experiment 1, bone ash values revealed that EcoPhos released an average of 0.72 g Ca/kg from Ca-deficient diets containing 1.1 g Ca/kg from soybean meal. Phytase supplementation in experiment 2 resulted in release of 1.07 g Ca/kg. In experiment 3, no differences were found in the relative bioavailability of Ca from feed-grade limestone, calcium citrate, calcium citrate-malate, or oyster shell, all relative to reagent-grade CaCO3. Calcium-deficient diets would benefit from either phytase supplementation or Ca supplementation from any of these-sources. (C) 2004 Elsevier Inc. All rights reserved.