Phytic acid is the main storage of P in plants, and most P in plant feed ingredients is bound in the phytate complex. Because pigs do not secrete phytase, an enzyme to hydrolyze inositol bonds in phytate, the utilization of P by pigs is very low. Addition of supplemental phytase to diets thus results in release of P and increases P utilization by pigs. However, all enzymes have a special recognition mechanism called specificity that works only with molecules that fit to active sites of the enzyme. Therefore, it is important to know how much of P is phytate-bound and how much of the P in a given diet is not phytate-bound.

Navarro Diego M. D. L., Jerubella J. Abelilla, and Hans H. Stein. 2019. Structures and characteristics of carbohydrates in diets fed to pigs: a review. Journal of Animal Science and Biotechnology, 2019, 10:39. Link to full text.