The presence of phytate in swine diets reduces the digestibility of calcium because phytate is able to bind calcium from organic sources and some inorganic sources, making it inaccessible to the pig. Microbial phytase breaks down phytate and increases the availability of calcium. An experiment was conducted to test the hypothesis that inclusion of microbial phytase increases the apparent (ATTD) and standardized (STTD) total tract digestibility of calcium in fish meal in diets containing phytate from corn and corn germ.
Besides phytate, corn and corn germ also add fiber and fat to diets, so it is important to know how fiber and fat affect calcium digestibility. Therefore, a second experiment was conducted to test the hypothesis that the values of ATTD and STTD of calcium obtained from cornstarch and corn based diets may differ, and to determine the effect of dietary fiber and fat on the ATTD and STTD of calcium in fish meal.