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.