Effects of increasing supplemental dietary Zn concentration on growth performance and carcass characteristics in finishing steers fed ractopamine hydrochloride

Abstract

Angus-cross steers (n = 288; 427 ± 0.4 kg) were utilized in a finishing study to evaluate the influence of increasing dietary Zn concentration on growth performance and carcass characteristics of steers fed ractopamine hydrochloride (RAC). In a randomized complete block design, steers were blocked by weight (6 steers/pen) and fed a dry-rolled corn-based diet for 79 d containing no supplemental Zn (CON; n = 8), 60 mg Zn/kg from ZnSO4 and no supplemental Zn-amino acid complex (ZnAA; ZnAA0; n = 8) or ZnAA0 diet supplemented with 60 (ZnAA60; n = 8), 90 (ZnAA90; n = 7), 120 (ZnAA120; n = 8), or 150 (ZnAA150; n = 8) mg Zn/kg DM from ZnAA. Thirty-one days prior to harvest (day 48 of study) all steers began receiving RAC at 300 mg⋅steer-1⋅d-1. This study was organized as 2 groups (GRP) of steers and groups were stagger started so that GRP1 started and ended 2 wk before GRP2. Pen was the experimental unit, and the statistical model included the fixed effects of treatment and block nested within GRP. Three a priori single degree of freedom contrasts were developed: linear and quadratic effects of ZnAA supplementation (ZnAA0, ZnAA60, ZnAA90, ZnAA120, and ZnAA150), and CON vs. Zn (CON vs. ZnAA0, ZnAA60, ZnAA90, ZnAA120, and ZnAA150). Dietary Zn concentration did not affect growth performance prior to RAC supplementation (P ≥ 0.17). During the RAC-period ADG and DMI were not affected by dietary Zn (P ≥ 0.16), while there was a linear effect of dietary Zn supplementation to decrease G:F (P = 0.04). Marbling scores were greatest in CON steers (P = 0.03). Liver Cu (day 45 and 80) and meat Cu (harvest) concentrations were greater in CON steers relative to Zn-supplemented steers (P ≤ 0.05), and plasma Zn linearly increased as dietary Zn increased (P = 0.007). Warner-Bratzler shear force was not different among treatments (P ≥ 0.25), and meat total collagen was quadratically affected by dietary Zn supplementation (P ≤ 0.002) where ZnAA0 was greatest. Overall, there was no effect of dietary Zn concentration on growth performance of RAC-supplemented steers in this study.

Effects of supplemental zinc sulfate on growth performance, carcass characteristics, and antimicrobial resistance in feedlot heifers1

“…Marbling scores were determined by camera imaging (VBG 2000, E+V Technology GmbH & Co. KG, Oranienburg, Germany); small = 400 to 499; modest = 500 to 599. carcass trait. Likewise, Genther-Schroeder et al (2018) observed no differences in carcass performance when steers were supplemented 0, 60, 90, 120, and 150 mg Zn/kg as Zn-amino acid complex to diets that contained 60 mg Zn/kg as Zn sulfate and a basal concentration of 30 mg Zn/kg DM. Steers supplemented 25 mg Zn/kg DM from Zn oxide or two forms of Zn proteinate had increased quality grades and increased marbling scores compared to un-supplemented steers, regardless of source (Spears and Kegley, 2002), when the basal ration contained 26 mg Zn/ kg DM.…”

Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0

“….. Outliers were determined using Cook's D statistic and removed if Cook's D > 0.5. One steer was determined to be an outlier for day 48 liver biopsy TM and data were removed' [58].…”

Effects of increasing supplemental zinc in beef feedlot steers administered a steroidal implant and beta agonist

“…Similarly, beta agonists induce rapid growth ( Johnson et al, 2014 ; Lean et al, 2014 ), albeit across a much shorter timeframe. This growth appears to be greatest early in the beta agonist feeding period ( Maxwell et al, 2015 ; Genther-Schroeder et al, 2018 ). Adequate Zn supplementation is vital to DNA synthesis ( Williams and Chesters, 1970 ) and results in increased phosphorylation of mTOR and FOXO ( Gao et al, 2014 ) indicative of Zns importance to protein synthesis and degradation.…”

“…Cattle were fed 1 of 4 Zn treatments ( n = 22 or 23 steers per treatment): 0, 100, 150, or 180 mg supplemental Zn/kg on a DM basis (Zn0, Zn100, Zn150, or Zn180, respectively) from ZnSO 4 administered daily through a dried distillers grains plus solubles-based premix in the total mixed ration ( TMR ). Zinc treatments were chosen to represent no supplemental Zn, industry supplementation of Zn ( Samuelson et al, 2016 ), and supranutritional concentrations of Zn previously supplemented in the literature ( Genther-Schroeder et al, 2018 ).…”