Determination of the relative bioavailability of potentiated zinc oxide in sheep

Thirty-six Polypay crossbred wether lambs (33.49 ± 2.81 kg) were used to determine the relative bioavailability of supplemental potentiated zinc oxide (PZO) in comparison to zinc sulfate (ZnSO4) and resulting effects on zinc (Zn) retention, nutrient digestibility, and nitrogen (N) balance. Wethers were sorted by body weight (BW) into three blocks and stagger-started on trial. On d -25 (relative to collection period start), wethers were housed in group pens and began a low-Zn diet (25 mg Zn/kg DM) that was fed for the entirety of the study. Wethers were moved to individual crates on d -10, where they acclimated for 5 d before dietary treatments began on d -5. Zinc treatments were top-dressed using ground corn as a carrier: 1) Control (CON)-no additional Zn supplementation; 2) HiZox® (PZO)-40 mg of supplemented Zn from a potentiated Zn oxide; and 3) Zinc sulfate (ZS) - 40 mg of supplemented Zn from ZnSO4. D 1 began a 5-d total collection period of feces and urine that was utilized for determination of Zn and N retention, as well as dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) digestibility. Blood was collected on d -5, before starting treatment, and on d 1 and d 5 of the collection period to assess circulating plasma Zn concentrations. Mineral solubility was evaluated, and filtrate Zn content was analyzed. Data were analyzed using the mixed procedure of SAS 9.4 (SAS Institute, Cary, NC). Contrasts compared CON vs. ZINC (PZO and ZS together) and the two Zn sources (PZO vs. ZS). Significance was declared at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. Dietary treatment did not affect DM, OM, or NDF intake, fecal output, or N intake, fecal and urinary output, and retention (mg/d and percent of intake; P ≥ 0.24). Nitrogen retention was greater in wethers supplemented with Zn (P = 0.02). Zinc intake, fecal output, retention (mg/d and percent of intake), and apparent absorption were greater for ZINC compared with CON (P ≤ 0.01) but did not differ between Zn sources (P ≥ 0.44). The inclusion of supplemental Zn improved N apparent absorption (P = 0.02), however, no differences were observed between Zn sources (P = 0.25). The PZO was less soluble in both solutions compared to the ZS (P ≤ 0.01). These data indicate the potentiated Zn oxide has a similar relative bioavailability compared to Zn sulfate and elicited similar effects on diet digestibility and N utilization.