The Effect of Corn-Expressed Phytase Supplementation in Adequate or Low Levels of Phosphorous and Calcium Diets on Growth Performance and Bone Ash of Nursery Pigs

This experiment was conducted to determine growth performance and metacarpal bone characteristics when nursery pigs fed phosphorus and calcium adequate or deficient diets were supplemented with varying levels of corn-expressed phytase (CEP; GraiNzyme® Phytase, Agrivida Inc., Woburn, MA). A total of 288 pigs were blocked by initial BW and allotted to 1 of 6 treatments (8 replicates per treatment). Pens were randomly assigned to dietary treatments. Treatments were: P/Ca adequate (PC; NRC, 2012) or low (NC: -0.15% P and -0.12% Ca) diets with or without CEP supplementation (1000 or 4000 FTU/kg) in both PC and NC diets fed in all 3 phases (14, 12, 14d). All of the pigs were euthanized at termination of phase 3 to collect metacarpal bones for ash determination. Data were analyzed using PROC MIXED procedures of SAS with treatments as fixed effect and initial BW block as random effect. Orthogonal contrasts were performed to determine the effects of increasing CEP. As CEP increased, phase-3 ADG, overall ADG, and BW increased linearly in pigs fed NC diets when compared to the PC fed counterpart (Linear CEP x P/Ca level interaction; P < 0.05, Table 1). Similarly, G:F increased quadratically with increasing level of CEP in NC diet fed pigs (P < 0.05). Feeding the 4000 FTU/kg diet restored bone ash weight to levels similar to pigs fed adequate P/Ca. No Significant difference (P > 0.05) was seen for bone ash percentage as level of CEP increased. Results suggest that pigs fed diets low in P and Ca supplemented with CEP performed similar to pigs fed a diet with adequate levels of Ca and P.

Table 1. Mineral level by phytase interaction effects of corn-expressed phytase on growth performance and bone ash in nursery pigs
	Adequate Mineral				Low Mineral1				Mineral*Phytase P-values
Phytase, FTU/kg	0	1000	4000		0	1000	4000	SE	Interaction	Linear	Quadratic
BW Final, kg	21.51	21.23	21.28		20.26	21.13	22.02	1.12	0.10	0.05	0.43
ADG Phase3 kg/d	0.665	0.647	0.651		0.609	0.650	0.682	0.028	0.02	0.02	0.20
ADG Overall, kg/d	0.389	0.381	0.382		0.359	0.379	0.401	0.018	0.09	0.04	0.43
G:F Phase 3	0.695	0.677	0.668		0.633	0.698	0.676	0.017	0.04	0.13	0.04
Ash, g	0.92	1.02	1.04		0.77	0.85	0.97	0.06	0.23	0.10	0.60
Ash, %	25%	26%	26%		22%	24%	24%	0.01	0.25	0.16	0.37

¹P and Ca was reduced by 0.15 and 0.12%, respectively