Digestibility of Ca and P is most correctly determined as standardized total tract digestibility (STTD). Data for the STTD of P in most feed ingredients have been published, and the STTD of Ca has also been determined in many feed ingredients. However, in practical diet formulation, values for STTD of Ca and P obtained in growing pigs are also applied to sows although there is a lack of comparative data between growing pigs and sows.

Therefore, an experiment was conducted to test the hypothesis that no differences exist between gestating sows and growing pigs for basal endogenous losses, STTD, and retention of Ca and P.