Comparison of Trace Mineral Repletion Strategies to Overcome a High Antagonist Diet

The objective was to compare trace mineral (TM) repletion strategies after depletion by S and Mo. Seventy-two Red Angus steers were blocked by BW (254 ± 14 kg) and assigned equally (6 steers per pen, fed via GrowSafe bunks) to corn silage-based depletion period diets either supplemented with Cu, Mn, Se, and Zn at NRC recommendations (CON) or supplemented with 0.3% S (CaSO₄), 5 mg of Mo/kg DM, and no added TM (DEP). Ending depletion liver Cu, Mn, and Se concentrations were lesser (P < 0.0001) for DEP vs. CON, while Zn was not different (P = 0.28). On d 89 steers were equally divided within diet to one of three TM repletion strategies: 1) Multimin90 injection (contains Cu, Mn, Se, Zn) and 100% of NRC dietary TM supplementation from inorganic sources (ITM), 2) saline injection, and 150% of NRC from inorganic sources (ING), or 3) saline injection, and 150% of NRC provided as 25% organic and 75% inorganic sources (BLEND). Depletion steers received supplemental S and Mo throughout repletion. Liver TM was determined on d -9, 14, 28, and 42 of repletion period, and analyzed as repeated measures using Proc Glimmix (n = 12 per treatment). The interaction of depletion × repletion strategy × day was not significant for any variable (P ≥ 0.19). Liver Se (P < 0.0001) and Zn (P = 0.09) concentrations were lesser in DEP vs. CON throughout repletion. Depletion diet by day (P < 0.0001) affected liver Cu where CON did not differ across repletion (averaging 262 mg/kg DM), while DEP increased across all days, ending at 71 mg/kg DM. Repletion Cu and Se were affected by repletion strategy × day interactions (P < 0.0001) where d 0 and 42 values were similar across TM sources, d 14 ITM values were greater than other treatments, and d 28 ITM values were greater than ING, while BLEND tended to be (Cu) or was greater (Se) than ING. At the start of repletion, liver Mn concentrations were lesser in steers assigned to ITM than ING and BLEND (P ≤ 0.004); however, on d 14 ITM and ING steers had greater liver Mn than BLEND (P ≤ 0.04), with no differences on d 28 and 42. These data suggest that regardless of dietary antagonists, ITM repleted Cu and Se rapidly, while similar repletion took 28 d and 42 d for the BLEND and ING treatments, respectively.