Effects of injectable trace minerals on reproductive performance of beef heifers in adequate trace mineral status

Red Angus–based, May-born heifers (n = 799) at 2 locations (Maddux Ranches, Wauneta, NE) were used to evaluate an injectable trace mineral on reproductive performance. Following October weaning, heifers were backgrounded in a feedlot until reaching a BW of 295 kg and then moved to native range at location 1 (n = 125) or location 2 (n = 286) in early March. Additional heifers (n = 388) grazed corn residue with cows, weaned in April, and were backgrounded until reaching 295 kg and then transported to locations 1 and 2 by early June. Free-choice mineral was available at both locations. Initial liver mineral status before treatment (n = 22; 307 kg) was adequate and not different (P > 0.26) among winter locations (copper = 146 μg/g, manganese = 9.22 μg/g, selenium = 1.54 μg/g, and zinc = 115 μg/g). Heifers were synchronized with a 14-d controlled internal drug-release (CIDR) timed-AI protocol and injected with a trace mineral (5 mL, Multimin 90; MM, n = 399) or not (CON, n = 400) at CIDR insertion. Bulls were with heifers on range 60 d following AI. The proportion of heifers pregnant within the first 21 d was not different (P = 0.32; 69 vs. 62 ± 3%; CON vs. MM) nor were those pregnant within 33 d (P = 0.57; 86 vs. 77 ± 2%; CON vs. MM) or overall pregnancy rates (P = 0.38; 95 vs. 93 ± 1%; CON vs. MM). Injectable trace mineral 33 d before AI did not influence reproductive performance in heifers with adequate trace mineral status.