Table 5.

Calculated aP release values based on different response criteria¹,²

	Phytase, FTU/kg3						Probability, P-value
Item	150	250	500	1,000	1,500	SEM4	Linear	Quadratic
Performance
ADG	0.039	0.035	0.058	0.128	0.129	0.0187	<0.001	0.078
G:F	0.044	0.018	0.052	0.138	0.110	0.0163	<0.001	0.045
Bone characteristics4
Bone ash, g	−0.026	−0.008	0.032	0.074	0.182	0.0195	<0.001	0.138
Bone ash, %	−0.029	0.044	0.083	0.035	0.116	0.0339	0.008	0.721

¹The marginal intake of available P (aP) per day was calculated for each pen using the equation: aP intake/day = [dietary aP% - 0.11% (aP in the basal diet)] × ADFI. A standard curve was then developed for each response criterion using the marginal aP release as the predictor variable. The equation for the standard curve was used to calculate aP release from each pen fed the different phytase dosages based on the observed value for each response criterion.

²ADG = average daily gain. G:F = gain-to-feed ratio.

³GraINzyme, Agrivida, Woburn, MA.

⁴One pig per pen (nine pens per treatment) was euthanized on day 21, and the right fibula was collected to determine bone ash weight and percentage bone ash. Fibulas were autoclaved for 1 h. After cleaning, bones were placed in a drying oven at 105 °C for 7 d and then ashed in a muffle furnace at 600 °C for 24 h.