Effects of Copper, Zinc, and Manganese Source on Mineral Status, Reproduction, Immunity, and Calf Performance in Young Beef Females over a Two-Year Period123

Crossbred beef females (n = 43 nulliparous heifers, yr 1; n = 37 primiparous cows, yr 2) were used to evaluate the effects of Cu, Zn, and Mn source on mineral status, reproduction, immunity, and performance in young grazing cattle in Eastern Colorado over a 2-yr period. Pregnant nulliparous heifers were stratified by expected calving date, BW, body condition score (BCS), and liver mineral status and assigned to treatments, which included 1) organic (ORG; 50% organic and 50% inorganic Cu, Zn, and Mn) and 2) inorganic (ING; 100% inorganic CuSO4, ZnSO4, and MnSO4) trace minerals. Treatments were provided via ad libitum mineral feeders from 54 d (yr 1) and 81 d (yr 2) prior to the average calving date through 119 d (yr 1) and 135 d (yr 2) post-calving. Final liver Cu concentrations were greater (P<0.05), and final liver Mn concentrations tended to be greater (P<0.06), in females receiving ORG vs ING treatments. Estrous cyclicity tended (P<0.08) to be greater in ORG vs ING females, and there was a tendency (P<0.07) for greater pregnancy rate in ING vs ORG females after a 60-d breeding season. In pregnant heifers, concentrations of IgG antibody titers specific for porcine red blood cells (PRBC; injected i.m.) were greater (P<0.03) in ORG than in ING heifers on d 14, and total Ig titers specific for PRBC were greater (P<0.05) in ORG than in ING heifers on d 21.