Supplemental Trace Minerals (Cu, Mn, and Zn) As Sulfates or Hydroxychloride Sources for Beef Heifers

Crossbred-Angus heifers (n = 215, 249 ± 9 kg initial BW, 295 ± 16.5 d of age) were used over a 2-yr period to determine the effects of mineral source on beef heifer development at 2 locations (n = 71, Fayetteville, block 1; n = 72 in each of 2 breeding groups, Batesville, blocks 2 and 3). Within each breeding group, heifers were stratified based on initial BW, age, health, prior research project, and sire; and assigned to 6 groups of 12 heifers, groups were then assigned randomly to 1 of 2 trace mineral treatments. The 2 treatments were trace mineral supplementation (Cu [74 mg/d], Mn [294 mg/d], and Zn [221 mg/d]) as 1) sulfate or 2) hydroxychloride sources. Treatments were delivered through mineral and vitamin supplements provided free choice and formulated for a consumption rate of 113 g/d. Heifers were maintained on fescue-bermudagrass pastures and were rotated monthly to limit pasture effects. Treatments began on d 0, with the breeding season starting on d 112 (block 1, with a synchronization period and A.I for 10 d, followed by a 60 d exposure to bulls); d 130 (block 2, 60 d exposure to bulls); and d 146 (block 3, 60 d exposure to bulls); with the conclusion of the trial on d 224 (block 1), d 252 (block 2), and d 268 (block 3). During the trial, 28-d BW, mineral disappearance, health records, and reproductive efficiency data were recorded. At the end of each trial, pregnancy was confirmed by determining the presence of Pregnancy-Specific Protein B concentrations in blood. There were no treatment differences (P ≥ 0.52) detected in BW or ADG throughout the trial. There was a tendency for greater mineral disappearance in the sulfate treatment (P = 0.07) compared to the hydroxychloride treatment. Pinkeye occurrence was fewer (P = 0.04) in the sulfate treatment group compared to the hydroxychloride treatment (1.9% vs. 7.5%). There were no differences in the percentage of heifers treated for bovine respiratory disease (P = 0.56) or foot rot occurrence (P = 1.00) between sulfate and hydroxychloride treatments. Trace mineral source did not affect reproductive performance (P = 0.75). Therefore, supplementing sulfate or hydroxychloride sources of Zn, Mn, and Cu to developing beef heifers resulted in similar performance.