Bioavailability of zinc hydroxychloride relative to zinc sulfate in growing cattle fed a corn-cottonseed hull-based diet

Abstract

A study was conducted to evaluate the bioavailability of zinc hydroxychloride (ZnOHCl) relative to Zn sulfate (ZnSO4) in growing steers. Sixteen Angus and Simmental steers (371kg average initial weight) were fed a corn-cottonseed hull-based diet without supplemental Zn for 14d. At the end of the 14-d depletion phase steers were randomly assigned within a breed to treatments consisting of supplemental Zn at 25mg/kg DM from either ZnSO4 or ZnOHCl. Seven days after the initiation of Zn supplementation a 5-d total collection of feces and urine was conducted. Jugular blood samples were obtained on d 0 (prior to initiation of Zn treatments) and on d 40 of the study for plasma Zn determination. Dry matter intake, Zn intake and urinary Zn excretion were not affected (P>0.10) during the metabolism phase. Apparent absorption and retention of Zn were greater (P<0.01) in steers supplemented with ZnOHCl than in those supplemented with Zn SO4. Plasma Zn concentrations were similar across treatments on d 0 of the study. On d 40 of the study plasma Zn concentrations were higher (P<0.05) in steers supplemented with Zn OHCl compared to those fed ZnSO4. Results of this study indicated that ZnOHCl is a more bioavailable source of Zn than ZnSO4 for growing cattle when supplemented to a diet with relatively low Zn bioavailability.