LAUSR

Abstract Efficacy of Escherichia coli phytase (ASP) was evaluated in nursery pigs fed low Ca and digestible P corn and soybean meal diet. Piglets were weaned on day 21, fed a common commercial starter diet for 7 d, and assigned to pens (4 pigs/pen: 2 ♀ and 2 ♂) based on day 7 BW. Positive control (PC) and negative (NC) diets were formulated with similar energy and nutrients with exception of total Ca, total P, and digestible P concentrations being 79%, 67%, and 55% that of PC diet, respectively. Two other diets were formulated by adding ASP in NC at 500 and 1,000 FTU/kg. All diets had 0.2% TiO2 indigestible marker. The diets were allocated to pens to give 6 replicates per diet and fed for 42 d. Feed intake and body weight were monitored at 14-d intervals. On day 42, 1 pig/pen was bled and euthanized to access blood and tissue samples. Analyzed total Ca and P in NC diet was 71% and 69% of concentration in PC diet. Recovery of phytase in pelleted diets was 66.2% and 73.5% for NC+500 FTU/kg and NC+1,000 FTU/kg diets, respectively. Between days 15 and 42, pigs fed NC diet grew slower and ate less feed than pigs fed the other diets. Overall (days 0–42), phytase in NC increased (P ≤ 0.05) ADG linearly and quadratically. On day 42, pigs fed PC, NC+500 FTU/kg, and NC+1,000 FTU/kg were +6.1, +5.9, and +7.1 kg heavier (P < 0.05) than pigs fed NC, respectively. Pigs fed PC and NC plus phytase exhibited higher (P = 0.003) G:F relative to NC pigs between days 15 and 28. Pigs fed NC diet had lower (P < 0.001) plasma P concentration, apparent total tract digestibility (ATTD) of Ca and P, and metacarpal and metatarsal bone attributes than pigs fed any other diets. Supplementation of phytase in NC linearly increased (P < 0.05) plasma P concentration, ATTD of Ca and P, and bone attributes. Specifically, phytase increased (P ≤ 0.025) dry weight, length, and ash weight in metacarpals and metatarsals. In conclusion, low total Ca and digestible P diet depressed growth and P utilization in piglets. Supplemental phytase improved performance in pigs fed NC linked to enhanced nutrients uptake and metabolism commensurate to pigs fed adequate total Ca and digestible P from inorganic source.