Effects of supplemental zinc, copper, and manganese concentration and source on performance and carcass characteristics of feedlot steers.

Abstract Text: Four-hundred cross-bred steers (initial BW 335 ± 9.6 kg) were utilized to investigate the effects of supplemental Zn, Cu, and Mn concentration and source on performance and carcass characteristics of feedlot steers fed a high concentrate steam flaked corn-based finishing diet for 159 d and zilpaterol hydrochloride for the last 21 d prior to slaughter (5-d withdrawal). The experimental design was a randomized complete block design. Steers were blocked by weight and randomly assigned within block to one of the 5 treatments (8 pens/treatment; 10 hd/pen). Treatments consisted of: 1) 90 mg of Zn/kg DM from ZnSO₄; 17.5 mg of Cu/kg DM from CuSO₄; 48 mg of Mn/kg DM from MnSO₄; 2) 30 mg of Zn/kg DM from  Zn Hydroxychloride; 10 mg of Cu/kg DM from basic Cu chloride ; 20 mg of Mn/kg DM from  Mn Hydroxychloride; 3) 45 mg of Zn/kg DM from Hydroxychloride; 12.5 mg of Cu/kg DM basic Cu chloride; 29.5 mg of Mn/kg DM from Mn Hydroxychloride; 4) 60 mg of Zn/kg DM from Zn Hydroxychloride; 15 mg of Cu/kg DM from basic Cu chloride; 39 mg of Mn/kg DM from Mn Hydroxychloride ; and 5) 90 mg of Zn/kg DM from Zn Hydroxychloride; 17.5 mg of Cu/kg DM from basic Cu chloride; 48 mg of Mn/kg DM from Mn Hydroxychloride. Steers were individually weighed on d−1, 0, 55, 112, and pen weighed two consecutive days at the termination of the experiment. Steers were transported to a commercial abattoir, slaughtered, and individual carcass data and liver samples were collected. Initial pen BW was used as a covariate in the statistical analysis and significance was determined at P ≤ 0.05. No differences were observed for final body weight (P> 0.42). Overall ADG, DMI, and feed efficiency were similar across treatments. Hot carcass weight, dressing percentage, yield grade, LMA, adjusted fat thickness, KPH, and marbling score were similar across treatments. Concentrations of Zn, Cu, and Mn in livers and blood samples collected on d 112 and at harvest were similar across treatments. These data indicate that under the conditions of this experiment, supplemental Zn, Cu, and Mn concentration and source had no impact on performance and carcass characteristics in feedlot steers. 

Keywords: Cattle, feedlot, trace mineral