Effects of Feeding Corn-Expressed Phytase on the Live Performance, Bone Characteristics, and Phosphorus Digestibility of Nursery Pigs.

A 41-day feeding trial was conducted to determine the efficacy of a corn-expressed phytase (CEP; Grainzyme^®, Agrivida) on the live performance, bone characteristics and P digestibility of nursery pigs fed a reduced P diet. Weaned piglets (21 ± 3 days; n=360) were acclimated on a common diet (phase 1) for 7 days before randomization into 60 single-sex pens containing 6 pigs (6.6 ± 1.2 kg) per pen. Six treatments were fed: positive control (PC; 0.4 or 0.32% aP for phase 2 or 3 and 4, respectively), negative control (NC; 0.15% reduced aP), and 500, 1000, 2000, or 4000 FTU CEP/kg added to NC in a 3-phase feeding program. Pigs were weighed on d 0, 14, 28, and 41, and feed disappearance recorded per phase. Apparent total tract digestibility (ATTD) of P was determined by feeding chromic oxide marker (d 28 to 35) and collecting fecal samples on d 35. On d 41, 4 pigs per pen were euthanized and metacarpal bones were collected to evaluate bone breaking strength (BBS) and ash. Data were analyzed using PROC GLM of SAS (block, sex, treatment and sex by treatment interaction). Treatment Least Squares Means were separated, and linear, quadratic, and cubic treatment effects evaluated. Pigs fed 500 FTU CEP/kg had increased (P < 0.05) ADG (450 vs 395 g/d) and ADFI (668 vs 581 g/d) compared to NC pigs and equivalent (P > 0.05) ADG (473 g/d) and ADFI (686 g/d) as PC pigs from d 0 to 41. Pigs fed 500 FTU CEP/kg had higher ATTD of P (57%; P < 0.05) than both NC (32%) and PC (38%) pigs. Pigs fed 500 FTU CEP/kg had higher BBS (31 vs 40 kg/cm²) and bone ash weight (1.41 vs 1.11 g) than NC (P < 0.05). Pigs fed 1000 FTU CEP/kg had equivalent BBS (45 kg/cm²) and ash weight (1.51 and 1.56 g) as PC (P > 0.05). Pigs fed 4000 FTU CEP/kg had higher d 0 to 41 ADG (509 vs 473 g/d) and bone ash weight (1.72 vs 1.56 g) compared to PC (P < 0.05). There were linear (P < 0.0001) increases in ADG, ADFI, ATTD of P, BBS and bone ash characteristics as CEP inclusion increased. In conclusion, 500 FTU CEP/kg improved growth, ATTD of P, BBS and bone ash when added to a reduced P diet and 4000 FTU CEP/kg increased growth beyond the PC treatment.