Most swine diets must be supplemented with calcium because most plant ingredients commonly used in diets for pigs contain relatively little calcium. One way to add calcium is to include inorganic sources such as dicalcium phosphate or calcium carbonate; however, animal ingredients such as meat byproduct meals can also be used. These ingredients, often used as a protein source, are also a good source of calcium. To our knowledge, values for apparent (ATTD) and standardized (STTD) total tract digestibility of calcium in animal sources have not been reported. Therefore, an experiment was conducted to determine the ATTD and STTD of calcium in four calcium sources of animal origin.

The secondary objective of the study was to test the hypothesis that the addition of microbial phytase to diets containing calcium sources of animal origin would increase the digestibility of calcium. Although animal sources do not contain phytate, swine diets are composed primarily of plant ingredients, and the phytate in those ingredients might form complexes with the calcium in the animal sources.