24 Determining the phosphorus release of Smizyme TS G5 2,500 phytase in nursery pigs

Abstract

Abstract Two nursery trials (DNA 241×600) with 320 or 280 pigs, respectively (initially 10 kg) were used to determine the available P (aP) release curve for Smizyme TS G5 2,500 (Origination, Inc., Saint Paul, MN). Pigs were weaned at approximately 21-d of age, randomly allotted to pens based on initial body weight (BW) and fed a common diet. On d 21 post-weaning, pens were blocked by BW and randomly allotted to 1 of 8 (Exp. 1) or 7 (Exp. 2) dietary treatments with 5 pigs/pen and 8 pens/treatment. Treatments were formulated to include increasing aP from either inorganic P (0.12%, 0.18%, or 0.24% in Exp. 1 and 0.11%, 0.19%, or 0.27% in Exp. 2 from monocalcium P) or increasing phytase (150, 250, 500, 750, or 1,000 FTU/kg in Exp. 1 and 250, 500, 1000, or 1,500 FTU/kg in Exp. 2). Prior to beginning the 21-d studies, all pigs were fed the lowest inorganic P diet for a 3-d period. At the conclusion of the experiments, the pig closest to the pen mean BW was euthanized and the right fibula was collected to determine bone ash. In both experiments, pigs fed increasing aP from inorganic P had increased (linear, P< 0.01) ADG, G:F, and final BW. Additionally, pigs fed diets with increasing phytase had increased (Exp. 1 linear, P< 0.01, Exp. 2 linear and quadratic, P< 0.05) ADG, ADFI, and G:F. The aP release increased for ADG (Exp. 1 linear, P< 0.01; Exp. 2 linear and quadratic, P< 0.01), G:F (linear, P< 0.01), and bone ash percent (Exp. 1 linear and quadratic, P< 0.05; Exp. 2 linear, P< 0.01) up to the highest phytase inclusion. When combining the release values from Exp. 1 and 2, the release equations for Smizyme TS G5 2,500 are aP=(0.197×FTU)÷(584.956+FTU), aP=(0.175×FTU)÷(248.348+FTU), and aP=(0.165×FTU)÷(178.146+FTU) for ADG, G:F, and bone ash percent, respectively.