Fecal Mineral and Phytase Analysis

The fecal samples were oven-dried to a constant weight and ground to pass through a 0.5-mm screen before analysis. The dietary and fecal samples were dried at 105 °C in an oven for 4 h for dry matter determination (method 934.01; AOAC International, 2006 ). Titanium, Ca, and P were determined by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES; Optima TM 8000, PerkinElmer, Shelton, USA; method 985.01; AOAC International, 2006 ) after microwave digestion. Urine samples (10 mL) were dried at 60 °C before the microwave digestion. Plasma Ca and P were analyzed on a chemistry analyzer (AU480, Beckman Coulter, Brea, USA). The phytase activity was determined by colorimetric measurement of the released phosphate from phytate. One phytase unit was defined as the amount of enzyme that releases 1 µmol of inorganic phosphate from 50 mM phytate per min at 37 °C and pH 5.5. These analyses were performed in duplicate, except that phytase activity in the feed samples was determined from three replicates.