Four experiments for this thesis were conducted to characterize organic Zn sources chemically, and study their bioactivities for dairy cows and modes of action. Experiment 1. Studies on chemical characteristic of organic Zinc sourcesMineral concentrations, amino acid contents, structural characteristics, solubilities, complexed Zn percentages in soluble fractions of Zn sources in pH2, 0.2M HC1-KC1 buffer, pH5, 0.1M KH_2PO_4-K_2HPO_4 buffer and deionized water, and complex quotients (Q_f) of seven Zn sources...