45 Determining the Phosphorus Release Curve for Smizyme TS G5 2,500 Phytase from 500 to 2,500 FTU/kg in Nursery Pig Diets

Abstract

Abstract A total of 320 pigs (Line 241 × 600, DNA, Columbus, NE; initially 11.9 ± 0.22 kg) were used in a 21-day growth study to determine the available P (aP) release curve for Smizyme TS G5 2,500 (Barentz, Woodbury, MN). At approximately 19 d of age, pigs were weaned, randomly allotted to pens, and fed common starter diets for 18 d. Pigs were then 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 ingredients including phytase, monocalcium P, limestone, and sand were added to create the treatment diets. Treatments included 3 diets containing increasing inorganic P from monocalcium P (0.11, 0.19, and 0.27% dietary aP), or 5 diets with increasing phytase (500, 1,000, 1,500, 2,000, or 2,500 FTU/kg) added to the diet containing 0.11% aP. All diets were corn-soybean meal-canola meal-based and were formulated to contain 1.24% SID Lys, 0.30% phytate P, and an analyzed Ca:P ratio of 1.10:1. At the conclusion of the study, 1 pig closest to the mean BW of each pen was euthanized and the right fibula, 10th rib, and metacarpal were collected to determine bone ash, density, and total bone P. For bone ash, bones were processed using the non-defatted method. Residual bone ash was digested using nitric acid and P measured using Inductively Coupled Plasma Mass Spectrometry. For the overall experimental period, pigs fed increasing inorganic P had increased (quadratic, P ≤ 0.053) ADG, ADFI, G:F and final BW (Table 1). Pigs fed increasing phytase had increased (quadratic, P ≤ 0.004) ADG, G:F, and final BW and increased (linear, P = 0.019) ADFI. For fibula, rib, and metacarpal characteristics, pigs fed increasing aP from inorganic P had increased (linear, P < 0.001) bone ash weight, bone ash percentage, bone density, and bone P. Additionally, pigs fed increasing phytase had increased (P < 0.05) bone ash weight, bone ash percentage, bone density, and bone P in either a linear or quadratic manner depending upon bone. The aP release curve developed for Smizyme TS G5 2,500 for percentage bone ash using combined data generated from all three bones is: aP = (0.219 × FTU/kg) ÷ (993.238 + FTU/kg).