64 Determining the Phosphorus Release Curve for Sunphase HT Phytase from 250 to 2,000 FTU/kg in Nursery Pig Diets

Abstract

Abstract A total of 280 pigs (DNA 241 × 600, initially 10.4 ± 0.24 kg BW) were used in a 21-day growth study to determine the available P (aP) release curve for Sunphase HT phytase (Wuhan Sunhy Biology Co., Ltd., Wuhan, P.R., China). At approximately 19 d of age, pigs were weaned, randomly allotted to pens, and fed common starter diets. 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 7 dietary treatments with 5 pigs per pen and 8 pens per treatment. Dietary treatments were derived from a single basal diet and ingredients including phytase, monocalcium P, limestone, and sand were added to create the treatment diets. Treatments included 3 diets containing increasing (0.11, 0.19, and 0.27% aP) inorganic P from monocalcium P, or 4 diets with increasing phytase (250, 500, 1,000, or 2,000 FTU/kg) added to the diet formulated to 0.11% aP. All diets were corn-soybean meal-canola meal-based and were formulated to contain 1.24% SID Lys and an analyzed Ca:P ratio of 1.10:1. Before the beginning of the study, all pigs were fed a diet containing 0.11% aP for a 3-d period (d 18 to 21 post-weaning). At the conclusion of the study, 1 pig, closest to the mean weight of each pen, was euthanized and the right fibula, rib, and metacarpal were collected to determine bone ash and density. After cleaning, bones were submerged in ultra-purified water under vacuum for 4 h. Weights were then collected, and bone density was calculated. For bone ash, bones were placed in a drying oven at 105oC for 7 d and then ashed in a muffle furnace at 600oC for 24 h (Table 1). For the overall experimental period, feeding increasing levels of aP from inorganic P improved (linear, P ≤ 0.014) ADG, G:F, and final BW. Similarly, feeding increasing phytase increased (linear, P ≤ 0.011) ADG and final BW as well as improved (quadratic, P = 0.023) G:F. For fibula bone ash weight and percentage bone ash, rib bone ash weight and bone density, and all metacarpal bone properties, pigs fed increasing levels of aP from inorganic P exhibited a linear improvement (P ≤ 0.019), with a quadratic response (P ≤ 0.030) for fibula bone density and rib percentage ash. Additionally, pigs fed increasing phytase had increased (P < 0.05) bone ash weight, percentage bone ash, and bone density in either a linear or quadratic fashion depending on the bone analyzed. The available P release curve generated for Sunphase HT phytase for percentage bone ash combining values from right fibula, rib, and metacarpal is: aP = (0.360 × FTU) ÷ (2,330.250 + FTU).