Because commercial macromineral sources generally contain high concentrations of microminerals, especially Fe and Mn, refined sources of Ca and P (Ca carbonate and Na dibasic phosphate) were used to prevent interactions of the contaminants with the utilization of Zn and the other trace minerals. The remaining trace minerals added to all diets were provided as inorganic salts, except Se that was added as selenomethionine
in yeast protein (Sel-Plex; Alltech Inc.).