Effects of Lifetime Copper, Zinc, and Manganese Supplementation and Source on Performance, Mineral Status, Immunity, and Carcass Characteristics of Feedlot Cattle12

Two calf crops (n = 140, yr 1; n = 130, yr 2) from the same cowherd were used to evaluate the effects of lifetime Cu, Zn, and Mn supplementation and source on performance, status, immunity, and carcass traits of feedlot cattle. Dams were supplemented with trace mineral treatments from approximately 80 d pre-calving through 120 d post-calving. Treatments included 1) control (no supplemental Cu, Zn, or Mn), 2) organic (ORG; 50% organic and 50% inorganic Cu, Zn, and Mn), or 3) inorganic (ING; 100% inorganic CuSO4, ZnSO4, and MnSO4) trace minerals. In the feedlot, calves were maintained on the same treatments, except that ORG contained 33% organic and 67% inorganic Cu, Zn, and Mn. Cattle received a growing diet for 56 d and a finishing diet for 140 d (yr 1) and 145 or 181 d (yr 2) prior to harvest. There was a tendency for a growing-phase year × treatment interaction (P=0.10), and a finishing-phase year × treatment interaction was present (P<0.04) for BW gain to feed ratio (G:F). In yr 1, G:F was greater (P<0.05) in ORG cattle than in ING cattle during both feeding phases; non-supplemented controls had a greater (P<0.01) finishing phase G:F than did supplemented cattle. Supplemented cattle had greater (P<0.01) liver Cu concentrations than non-supplemented controls throughout both feeding phases, and liver Mn concentrations were greater (P<0.02) in supplemented cattle than in non-supplemented controls at the end of the finishing phase.