Vanessa Lagos, a Ph. D. candidate from the Stein Monogastric Nutrition lab, presents the results of an experiment designed to test whether ratios between STTD calcium and STTD phosphorus derived from multiple short-term studies of pigs at different stages of development may be applied to pigs fed diets without or with microbial phytase from 11 to 130 kg. Adapted from a presentation at the 2020 ASAS Midwestern Section meeting, Omaha, NE, March 2-4.