It is important that the digestibility of Ca in Ca sources is known to formulate diets based on values for digestible Ca rather than total Ca. Only a small amount of the Ca required by pigs is provided by plant-based ingredients and supplementation of Ca from Ca phosphates and Ca carbonate, is usually required to meet the requirement by pigs. In addition, use of microbial phytase increases Ca digestibility in Ca carbonate, which is one of the major sources of Ca in pig diets.

Differences in Ca digestibility in 4 sources of Ca carbonate produced in the United States have been observed, but it is unknown if there are differences in the ATTD of Ca in calcium carbonate sources produced outside the United States. Therefore, the objective of this experiment was to test the hypothesis that there are differences in the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of Ca and in the response to microbial phytase among 20 sources of Ca carbonate obtained from different parts of the world.