Evaluation of Absorption and Post-Absorptive Metabolism of Inorganic and Organic Zinc Sources

Abstract

A series of experiments was conducted to examine the absorption and post-absorptive metabolism of zinc (Zn) from inorganic and organic sources. Results of an in vivo experiment, using Holstein bull calves as models, suggested that, when Zn was supplemented at 20 mg Zn/kg DM for 98 d, Zn source had minimal impact on plasma or tissue Zn concentrations. However, when Zn was supplemented at 500 mg Zn/kg DM for 12 d, plasma and tissue Zn concentrations were greater in bulls that received Zn proteinate (ZnProt) than in those that received ZnSO and Ca only, uptake and transport of Zn from inorganic and organic Zn sources were similar. However, when added at high concentration in the presence of dietary antagonists, Zn uptake from organic sources appeared to be greater than from inorganic sources. Further research is certainly warranted to more clearly define differences in Zn absorption that may exist between inorganic and organic Zn sources at different dietary levels.