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A total of 184 pigs (10.3 and 9.7 kg BW, respectively) were used in two experiments to develop an available P (aP) release curve for commercial phytase products. In Exp. 1 and 2, pigs were fed a basal diet (0.06% aP) and 2 levels of added aP from inorganic P (monocalcium P) to develop a standard curve. In Exp. 1, 100, 175, 250, or 500 phytase units (FTU)/kg Phytase-1 or 200, 350, 500 or 1,000 FTU/kg Phytase-2 was added to the basal diet. In Exp. 2, 250, 500, 750, or 1,000 FTU/kg Phytase-1; 500, 1,000, or 1,500 FTU/kg Phytase-2; or 1,850 or 3,700 FTU/kg Phytase-3, was added to the basal diet. Manufacturer guaranteed phytase levels were used in diet formulation. Pigs were blocked by sex and weight and allotted to individual pens with 8 pens per treatment. Pigs were euthanized on d 21, and fibulas were analyzed for bone ash.
In Exp. 1, pigs fed increasing monocalcium P had improved (linear; P = 0.01) ADG, G/F, and percentage bone ash. Similarly, pigs fed increasing monocalcium P in Exp. 2 tended to have improved (quadratic; P = 0.09) ADG in addition to significantly improved (linear; P ≤ 0.001) G/F and percentage bone ash. In Exp. 1, pigs fed increasing Phytase-1 had increased (linear; P ≤ 0.02) ADG, G/F, and percentage bone ash. Likewise, pigs fed increasing Phytase-1 in Exp. 2 had improved (linear; P ≤ 0.001) ADG and G/F, as well as increased (quadratic; P ≤ 0.001) percentage bone ash. In Exp. 1, pigs fed increasing Phytase-2 had increased (linear; P ≤ 0.04) ADG and G/F and tended to have improved (linear; P = 0.06) percentage bone ash. Pigs fed increasing Phytase-2 in Exp. 2 had increased (quadratic; P ≤ 0.001) G/F and percentage bone ash. In Exp. 2, pigs fed increasing Phytase-3 had improved (linear; P ≤ 0.001) ADG in addition to increased (quadratic; P ≤ 0.03) G/F and percentage bone ash. When AOAC analyzed values and bone ash are used as the response variable, aP release for up to 1,000 FTU/kg of Escherichia coli-derived phytases (Phytase-1 and Phytase-2) can be predicted by the equation (y = -0.000000125x2 + 0.000236245x + 0.015482000), where x is the phytase level in the diet.
CK Jones, MD Tokach, BW Ratliff, NL Horn, SS Dritz, RD Goodband, JM DeRouchey, and JL Nelssen. 2009. Swine Day, Kansas State University. 106-121.
