Supplemental Trace Minerals (Zn, Cu, and Mn) as Sulfates or Hydroxy Trace Mineral Sources for Beef Heifers

Crossbred heifers (n = 286, 255 ± 4.5 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 and n = 72, Fayetteville, blocks 1 and 4; n = 72 in each of 2 breeding groups, Batesville, blocks 2 and 3). Heifers were stratified based on initial BW, age, health, prior research projects, and sire, and then assigned to 6 groups of 12 heifers, that were 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. Treatments began on d 0, and the breeding season began on d 112 and d 105 (blocks 1 and 4 respectively). After a synchronization period and a 10 d eligible period for artificial insemination, heifers were exposed to bulls for 50 d. At d 130 (block 2) and d 146 (block 3) heifers were exposed to bulls for 60 d. The trail concluded on d 224 (block 1), d 227 (block 4), d 252 (block 2), and d 268 (block 3). During the trial, BW at 28-d intervals, mineral disappearance, health records, and reproductive efficiency data were recorded. At the end of each trial, pregnancy was confirmed by the presence of Pregnancy-Specific Protein B concentrations in blood. No treatment differences (P ≥ 0.52) were detected in BW or ADG. There was no significance for greater mineral disappearance between mineral sulfate and hydroxychloride treatments (P = 0.46) There were no differences in the percentage of heifers treated for bovine respiratory disease (P = 0.77) or foot rot occurrence (P = 0.57) between sulfate and hydroxychloride treatments. Trace mineral source did not affect overall pregnancy rates (P = 0.85). Therefore, supplementing either a sulfate or hydroxychloride source of Zn, Cu, and Mn to developing beef heifers resulted in similar performance