Effect of Injectable Trace Mineral on Reproductive Performance in Beef Heifers

Red Angus-based, May-born heifers (n = 799) at 2 locations were utilized to determine the effects of an injectable trace mineral on reproductive performance. Heifers were managed at the Maddux ranch near Wauneta, NE. Following weaning in October, heifers were backgrounded in a feedlot until a BW of 295 kg was reached and then moved to graze native range at location 1 (L1; n = 125) or location 2 beginning in early March (L2; n = 286). A subset of heifers (n = 388) grazed corn residue with cows over winter, weaned in April, and backgrounded in a feedlot until target weight was attained and then transported to L1 and L2 finishing in early June. Heifers were offered free choice mineral at both locations. Initial mineral status was analyzed via liver biopsy prior to mineral treatment (n = 22; 307 kg). Initial liver concentrations of copper (146 µg/g), manganese (9.22 µg/g), selenium (1.54 µg/g), and zinc (115 µg/g) were adequate and not different (P > 0.26) among heifers managed at the 2 overwinter locations. Heifers were synchronized with a 14-d CIDR-prostaglandin F_2α protocol and either injected with a trace mineral (5 ml; MULTIMIN; n = 399) or received no injection (CON; n = 400) the day of CIDR insertion. Fertile bulls were placed with heifers on range for 60 d following AI. Pregnancy diagnosis was determined via transrectal ultrasonography 61 d post-AI. Heifer BW at pregnancy diagnosis was 333 and 342 kg; L1 and L2, respectively. The proportion of heifers pregnant within the first 21 d of the breeding season was not different (P = 0.32; 69 vs. 62 ± 3%; CON, MULTIMIN) nor was proportion pregnant within the first 33 d (P = 0.57; 86 vs. 77 ± 2%; CON, MULTIMIN). Bulls remained with heifers at initial ultrasound; therefore, a second pregnancy diagnosis was performed 30 d later. Overall pregnancy rates were also not different (P = 0.38; 95 vs. 93 ± 1%; CON, MULTIMIN). In summary, injectable trace mineral at CIDR insertion did not influence heifer reproductive performance in heifers with adequate trace mineral status.