Determination of available and total tract digestible phosphorus release curves for Microtech phytase.

A total of 320 barrows (DNA 200 × 400; initially 10.7 ± 0.21 kg) were used in a 21-d growth trial to determine the available P (aP) and true total tract digestible P (TTTD P) release curves for Microtech phytase (VTR Bio-Tech Co, Ltd, Guangdong, China). At ∼21 d of age, pigs were weaned, randomly allocated to pens and fed a common diet for 18 d and then fed a P deficient diet with 0.11% aP and 0.20% standardized total tract digestible (STTD P) for 3 d. On d 21 post-weaning, considered d 0 of the study, pigs were blocked by average pen body weight (BW) and randomly allotted to 1 of 8 dietary treatments with 5 pigs per pen and 8 pens per treatment. Dietary treatments were derived from a single basal diet and phytase, monocalcium phosphate, limestone, and sand were added to create the treatment diets. The basal diet was formulated to contain 0.32% phytate P. Treatments included 3 diets with 0.11%, 0.19% and 0.27% aP (corresponding to STTD P of 0.20%, 0.27% and 0.35%) using monocalcium phosphate and 5 diets with 0.11% aP (0.20% STTD P) and increasing phytase (250, 500, 1000, 1500 and 2000 FTU/kg). On d 14 of the trial, fecal samples were collected from 3 pigs per pen. Samples were analyzed for dry matter (DM), N, P, and TiO