Lay Summary Exogenous phytase is used to release the undigestible P in swine feed. Several phytase sources are commercially available and knowing their P release curve is important for effective use in diet formulations. Dietary phosphorus requirement estimates are defined as either available P or digestible P. Available P accounts for P that is digested, absorbed, and utilized for bone mineralization, whereas digestible P measures the difference between P intake and excretion adjusting for endogenous losses. Available and digestible P release of phytase depends on bone characteristics measured, type of bone used, and methodology used to estimate P digestibility. A novel phytase source, Microtech phytase, has limited data on its P release. Results from this study suggest that this phytase source improved growth performance, P digestibility and bone characteristics of nursery pigs. The use of 250 to 2,000 FTU/kg of Microtech phytase allows for 0.03 to 0.15% available P release or 0.02 to 0.09% digestible P release.
Navales et al. (Tue,) studied this question.