SUPPLEMENTAL PHYTASES OF MICROBIAL AND CEREAL SOURCES IMPROVE DIETARYPHYTATE PHOSPHORUS UTILIZATION BY PIGS FROM WEANING THROUGH FINISHING

This experiment was conducted to measure the nutritional and metabolic responses of pigs fed diets with continuous supplementation of microb ial and cereal phytase from weaning to finishing, and to determine the feasibility of complete replacement of inorganic P addition by supple mental phytase in swine diets. Forty-eight Landrace x Hampshire x Meis han pigs were divided into four groups. In phase 1 (10 to 50 kg BW), p igs in Groups 1, 2, 3, and 4 were fed a low-P, corn-soybean meal basal diet (ED), the ED plus microbial phytase (A. ficuum) at 1,200 units/k g, the ED plus 10% wheat bran (230 units of cereal phytase/kg), and th e ED + .24% inorganic P (calcium phosphate), respectively. In phase 2 (51 to 90 kg BW), these pigs were fed a similar ED or the ED plus 1,00 0 microbial phytase units/kg, 20% wheat bran, or .20% inorganic P, res pectively. Repeated measures included growth performance, P, Ca, and N balance, metatarsal and metacarpal bone strength, serum concentration of inorganic P, Ca, and 1,25-dihydroxycholecalciferol, and serum alka line phosphatase activity. Pigs fed the ED supplemented with microbial phytase and pigs fed the ED supplemented with inorganic P showed almo st identical responses for all variables. Pigs fed the ED supplemented with cereal phytase also had responses for various measures that were similar to those of pigs fed microbial phytase or inorganic P, except for some differences in serum inorganic P concentrations and bone str ength in phase 1. Because of improvements in apparent digestibility of dietary P and N, fecal excretion of these two nutrients was reduced b y 31 to 62% (P < .05) in pigs fed the ED supplemented with phytase com pared with pigs fed inorganic P. It is physiologically feasible and en vironmentally advantageous to replace inorganic P with microbial or ce real phytase in corn-soybean meal diets for this type of pig through t he entire growing-finishing period.