Effects of supplemental zinc source and level on finishing performance, health, and carcass characteristics of beef feedlot steers

ABSTRACT Objective Our objective was to compare the effects of supplemental Zn sources and levels on health, growth, and carcass characteristics in finishing steers. Materials and Methods Crossbred steer calves (n = 1,502; initial BW = 297 ± 5 kg) were housed in 24 pens with 8 pens per treatment in a randomized complete block design. Treatments (100% DM) consisted of the following: (1) control: 10.6 mg/kg of Cu [72.2% Cu sulfate/27.8% Cu AA complex (AAC)], 37.8 mg/kg of Zn (77.6% Zn sulfate/22.4% Zn AAC), and 25.5 mg/kg of Mn (81.6% Mn sulfate/18.4% Mn AAC); (2) combination: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate/33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride); and (3) hydroxy: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride). Results and Discussion There were no significant differences in DMI, ADG, final BW, F:G, morbidity, or mortality ( P ≥ 0.28). Hot carcass weight, DP, and backfat were also unaffected ( P ≥ 0.32) by treatment. Increased level of Zn tended ( P = 0.13) to increase marbling score. There was a tendency for combination to have a larger LM area ( P = 0.14) and lower YG ( P = 0.10) compared with hydroxy. Implications and Applications Steers fed a lower level of Zn sulfate/AAC had similar performance compared with steers fed a higher level of Zn. Zinc hydroxychloride is equally effective as a Zn sulfate/Zn methionine combination when fed at 90 mg/kg.