Addition of microbial phytase to diets of young pigs.

Microbial phytase was added at concentrations of 0, 500, and 1,000 phytase units per gram (PU/g) to a diet that derived the majority of its phosphorus content from organic sources. In addition, a positive control diet was prepared by adding calcium phosphate to increase the total dietary phosphorus by 1.7 g/kg. Each diet was available ad libitum for 3 wk to nine individually penned pigs approximately 5 wk old and with an initial weight of 10.2 kg. Digestibility of phosphorus was estimated, using chromic oxide as an indicator, from fecal samples obtained during the 3rd wk of the trial. Blood serum and metatarsal bones were obtained at slaughter. The addition of the microbial enzyme resulted in increased rate and efficiency of gain, increased digestibility of dietary phosphorus, increased serum phosphorus, decreased serum alkaline phosphatase, and increased metatarsal ash and weight of metatarsal phosphorus. The response to dietary microbial phytase was similar to that resulting from feeding a diet containing 1.7 g/kg of additional phosphorus from calcium phosphate.