Interpretive Summary: Intrinsic phytase increases the digestibility of phosphorus in diets fed to growing pigs
By: Anne Kamiya, MS
Phytate-bound nutrients in plant foods are indigestible without the enzyme phytase. Phosphorus (P) is one such nutrient, usually bound in the form of phytic acid. Unfortunately, many animals, including pigs, are unable to produce enough enzymes to digest these nutrients. For this reason, addition of a phosphate supplement or microbial phytase to feed is a common compensatory strategy.
Some plant foods naturally contain intrinsic phytase, which assist in breaking down the indigestible phytate-bound nutrients. Whether these intrinsic phytases can break down phytate-bound nutrients in added ingredients however is largely unknown. In this recent Journal of Animal Science study, researchers evaluated whether grains with intrinsic phytase could increase the digestibility of P when they are combined with plant-based ingredients without intrinsic phytase. Apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of P were used to determine digestibility.
Forty-eight growing pigs were fed one of six diets: a corn and soy bean meal (SBM) diet, a hybrid rye diet, and a hybrid rye, corn and SBM diet, each formulated in two different ways (one with added microbial phytase and one without). Results indicated that the addition of hybrid rye with intrinsic phytase consistently increased the digestibility of P both with and without added microbial phytase, supporting the authors’ hypothesis.
There are two significant takeaways from this study. Firstly, reevaluating the digestibility of mixed feed when at least one ingredient contains intrinsic phytase is recommended. Secondly, the addition of grains with intrinsic phytase to pig feed may overall benefit the digestibility of phytate-bound P. Overall, expanded studies looking at the potential of including grains with intrinsic phytase in the feed of pigs and other animals is an area of future study.
The original article, Intrinsic phytase in hybrid rye increases the digestibility of phosphorus in corn and soybean meal in diets fed to growing pigs, is viewable in the Journal of Animal Science.