Influence of steroidal implants and zinc sulfate supplementation on growth performance, trace mineral status, circulating metabolites, and transcriptional changes in skeletal muscle of feedlot steers.

Angus-cross steers (n = 144; 362 kg ±â€…20.4) were used to determine the effect of Zn and steroidal implants on performance, trace mineral status, circulating metabolites, and transcriptional changes occurring in skeletal muscle. Steers (n = 6 per pen) were stratified by body weight (BW) in a 3 × 2 factorial. GrowSafe bunks recorded individual feed intake (steer as experimental unit; n = 24 per treatment). Dietary treatments (ZINC; eight pens per treatment) included supplemental Zn as ZnSO4 at 1) 0 (analyzed 54 mg Zn/kg DM; Zn0); 2) 30 mg/kg DM (Zn30); 3) 100 mg Zn/kg DM (Zn100). After 60 d of Zn treatment, steers received a steroidal implant treatment (IMP) on day 0: 1) no implant; NO; or 2) high-potency combination implant (TE-200, Elanco, Greenfield, IN; 200 mg TBA, 20 mg E2; TE200). BWs were taken at days -60, 0, and in 28 d increments thereafter. Liver biopsies for TM analysis and blood for TM, serum glucose, insulin, nonesterified fatty acids (NEFA), urea-N, and IGF-1 analysis were collected on days 0, 20, 40, and 84. Glucose, NEFA, and insulin were used to calculate the revised quantitative insulin sensitivity check index (RQUICKI). Linear and quadratic effects of ZINC were evaluated in SAS 9.4. Means for IMP were separated using the LSMEANS statement with the PDIFF option. Day -60 BW was a covariate for performance and carcass data. Growth performance, plasma, liver, and metabolite data were analyzed as repeated measures. TE200 tended to decrease plasma Zn by 8.4% from days 0 to 20 while NO decreased by 3.6% (IMP × day; P = 0.08). A tendency for a ZINC × day effect on G:F was noted (P = 0.06) driven by Zn30 and Zn100 decreasing significantly from period 0-28 to period 28-56 while Zn0 was similar in both periods. An IMP × day effect was noted for RQUICKI where (P = 0.02) TE200 was greater on day 40 compared to NO cattle, but by day 84 RQUICKI was not different between TE200 and NO. On day 20, increasing Zn supplementation linearly increased mRNA abundance (P ≤ 0.09) of protein kinase B (AKT1), mammalian target of rapamycin (mTOR), matrix metalloproteinase 2 (MMP2), and myogenic factor 5 (MYF5). In this study, Zn and implants differentially affected genes related to energy metabolism, satellite cell function, and TM homeostasis on days 20 and 84 postimplant. These results suggest steroidal implants increase demand for Zn immediately following implant administration to support growth and may influence insulin sensitivity in finishing cattle.

Steroidal implants are a commonly used growth-enhancing technology that improves the efficiency of beef production. Steroidal implants increase muscle growth via increased net protein synthesis and skeletal muscle hypertrophy. Various trace minerals (TM) are important in supporting growth and development. Zinc (Zn) is an essential TM that influences numerous enzymes, transcription factors, and is involved in nearly every signaling pathway in the body. Nutritionists routinely supplement Zn, amongst other TM, at concentrations greater than current recommendations. Previous work shows that increased Zn supplementation improves growth performance in steers given a steroidal implant. The objective of this study was to better understand the effects of steroidal implants and zinc sulfate supplementation on growth, carcass characteristics, TM status, blood metabolites, and skeletal muscle mRNA abundance. In this study, there is evidence that steroidal implant administration increases tissue Zn demand as plasma Zn decreases following implant administration when growth rates are greatest. Our results also provide preliminary data outlining the impact of zinc and steroidal implants on mRNA abundance of skeletal muscle gene expression.

Impact of an Injectable Trace Mineral Supplement on the Immune Response and Outcome of Mannheimia haemolytica Infection in Feedlot Cattle.

The study aimed to assess the impact of injectable trace mineral ("ITM"; Multimin90; Fort Collins, CO) supplementation on bacterial infection in cattle. Angus-crossbred steers (n = 32) were organized into two blocks by initial body weight. Steers were maintained on a ryelage and dry-rolled corn-based growing diet without supplementation of Zn, Cu, Mn, and Se for the duration of the study. The steers were transported 6 h, then randomized into three treatment groups: control received sterile saline ("CON"), ITM administered 1 day after transport (6 days before infection, "ITMPRE"), and ITM administered 2 days post infection (dpi) concurrent with antibiotic treatment ("ITMPOST"). Steers were infected with Mannheimia haemolytica on day 0, and all were treated with tulathromycin at 2 dpi. Plasma levels of Zn, Cu, and Se did not differ among treatments (P ≥ 0.74). Liver Se was higher in ITMPRE at 2 dpi (P < 0.05), and both ITM groups had higher liver Se at 5 dpi (P < 0.05) compared to CON. A time × treatment interaction was detected for liver Cu (P = 0.02). Clinical scores were lower (P < 0.05) in ITMPRE on 1 and 8 dpi and ITMPOST on 8 dpi compared to CON. Thoracic ultrasonography scores were lower in ITMPRE at 2 dpi compared to CON (P < 0.05) and ITMPOST (P < 0.1). No treatment effects (P > 0.10) were observed for bacterial detection from bronchoalveolar lavage (BAL) or nasopharyngeal swabs. At 5 dpi, both ITMPRE and ITMPOST showed higher frequencies of γδ T cells and NK cells in BAL compared to CON (P < 0.05). Before infection, leukocytes from ITMPRE steers produced more IL-6 (P < 0.01) in response to stimulation with the TLR agonist, Pam3CSK4. Use of ITM may be an effective strategy for improving disease resistance in feedlot cattle facing health challenges.

Dietary Zinc Supplementation in Steers Modulates Labile Zinc Concentration and Zinc Transporter Gene Expression in Circulating Immune Cells.

Zinc (Zn) is critical for immune function, and marginal Zn deficiency in calves can lead to suboptimal growth and increased disease susceptibility. However, in contrast to other trace minerals such as copper, tissue concentrations of Zn do not change readily in conditions of supplementation or marginal deficiency. Therefore, the evaluation of Zn status remains challenging. Zinc transporters are essential for maintaining intracellular Zn homeostasis, and their expression may indicate changes in Zn status in the animal. Here, we investigated the effects of dietary Zn supplementation on labile Zn concentration and Zn transporter gene expression in circulating immune cells isolated from feedlot steers. Eighteen Angus crossbred steers (261 ± 14 kg) were blocked by body weight and randomly assigned to two dietary treatments: a control diet (58 mg Zn/kg DM, no supplemental Zn) or control plus 150 mg Zn/kg DM (HiZn; 207 mg Zn/kg DM total). After 33 days, Zn supplementation increased labile Zn concentrations (as FluoZin-3 fluorescence) in monocytes, granulocytes, and CD4 T cells (P < 0.05) but had the opposite effect on CD8 and γδ T cells (P < 0.05). Zn transporter gene expression was analyzed on purified immune cell populations collected on days 27 or 28. ZIP11 and ZnT1 gene expression was lower (P < 0.05) in CD4 T cells from HiZn compared to controls. Expression of ZIP6 in CD8 T cells (P = 0.02) and ZnT7 in B cells (P = 0.01) was upregulated in HiZn, while ZnT9 tended (P = 0.06) to increase in B cells from HiZn. These results suggest dietary Zn concentration affects both circulating immune cell Zn concentrations and Zn transporter gene expression in healthy steers.

The influence of steroidal implants and manganese sulfate supplementation on growth performance, trace mineral status, hepatic gene expression, hepatic enzyme activity, and circulating metabolites in feedlot steers.

Angus-cross steers (n = 144; 359 kg ±â€…13.4) were used to assess the effect of dietary Mn and steroidal implants on performance, trace minerals (TM) status, hepatic enzyme activity, hepatic gene expression, and serum metabolites. Steers (n = 6/pen) were stratified by BW in a 3 × 2 factorial. GrowSafe bunks recorded individual feed intake (experimental unit = steer; n = 24/treatment). Dietary treatments included (MANG; 8 pens/treatment; Mn as MnSO4): (1) no supplemental Mn (analyzed 14 mg Mn/kg DM; Mn0); (2) 20 mg supplemental Mn/kg DM (Mn20); (3) 50 mg supplemental Mn/kg DM (Mn50). Within MANG, steers received a steroidal implant treatment (IMP) on day 0: (1) no implant; NO; or (2) combination implant (Revalor-200; REV). Liver biopsies for TM analysis and qPCR, and blood for serum glucose, insulin, non-esterified fatty acids, and urea-N (SUN) analysis were collected on days 0, 20, 40, and 77. Data were analyzed as a randomized complete block with a factorial arrangement of treatments including fixed effects of Mn treatment (MANG) and implant (IMP) using PROC MIXED of SAS 9.4 using initial BW as a covariate. Liver TM, serum metabolite, enzyme activity, and gene expression data were analyzed as repeated measures. No MANG × IMP effects were noted (P ≥ 0.12) for growth performance or carcass characteristic measures. Dietary Mn did not influence final body weight, overall ADG, or overall G:F (P ≥ 0.14). Liver Mn concentration increased with supplemental Mn concentration (MANG; P = 0.01). An IMP × DAY effect was noted for liver Mn (P = 0.01) where NO and REV were similar on day 0 but NO cattle increased liver Mn from days 0 to 20 while REV liver Mn decreased. Relative expression of MnSOD in the liver was greater in REV (P = 0.02) compared to NO and within a MANG × IMP effect (P = 0.01) REV increased liver MnSOD activity. These data indicate current NASEM Mn recommendations are adequate to meet the demands of finishing beef cattle given a steroidal implant. Despite the roles of Mn in metabolic pathways and antioxidant defense, a basal diet containing 14 mg Mn/kg DM was sufficient for the normal growth of finishing steers. This study also provided novel insight into how implants and supplemental Mn influence genes related to arginine metabolism, urea synthesis, antioxidant capacity, and TM homeostasis as well as arginase and MnSOD activity in hepatic tissue of beef steers.

Steroidal implants improve cattle growth and efficiency partially through increased net protein synthesis resulting in increased skeletal muscle hypertrophy. Necessary to support this increased growth are trace minerals (TM). Manganese (Mn) is essential, serving as a cofactor and activator of various enzymes. Manganese plays a crucial role in ruminant animals by supporting nitrogen recycling while also being essential for mitochondrial antioxidant defense. Consulting nutritionists routinely supplement Mn, amongst other TM, at concentrations greater than current recommendations. However, there is limited research on the impact of supplemental Mn in implanted finishing cattle. Our prior work suggests steroidal implants decrease liver Mn concentration. This is of interest as liver Mn concentration is tightly regulated. Therefore, this study evaluated the effects of steroidal implants and manganese sulfate supplementation on cattle growth performance, trace mineral status, expression of relevant hepatic genes, hepatic enzyme activity, and circulating metabolites in feedlot steers. In this study, supplementing Mn at the recommended concentration did not influence the growth of both implanted and non-implanted cattle.

Effects of feeding a Saccharomyces cerevisiae fermentation product and ractopamine hydrochloride to finishing beef steers on growth performance, immune system, and muscle gene expression.

The objective of this study was to determine impacts on immune parameters, anti-oxidant capacity, and growth of finishing steers fed a Saccharomyces cerevisiae fermentation product (SCFP; NaturSafe; Diamond V, Cedar Rapids, IA) and ractopamine hydrochloride (RAC; Optaflexx; Elanco Animal Health, Greenfield, IN). Angus-crossbred steers (N = 288) from two sources were utilized in this 90-d study. Steers were blocked by source, stratified by initial body weight to pens of six steers, and pens randomly assigned to treatments (16 pens per treatment). Three treatments compared feeding no supplemental SCFP (control; CON) and supplemental SCFP for 57 d (SCFP57), and 29 d (SCFP29) before harvest. Supplementation of SCFP was 12 g per steer per d, and all steers were fed RAC at 300 mg per steer per d for 29 d before harvest. Blood samples were collected from3 steers per pen, and muscle samples were collected from 1 steer per pen at 57, 29 (start of RAC), and 13 (midRAC) days before harvest. Blood was analyzed from 2 steers per pen for ferric reducing anti-oxidant power (FRAP). Muscle gene expression of myokines, markers of anti-oxidant and growth signaling were assessed. Individual animal BW were also collected on 57, 29, 13, and 1 d before being harvested at a commercial facility (National Beef, Tama, IA). Data were analyzed using the Mixed procedure of SAS 9.4 (Cary, NC) with pen as the experimental unit. The model included fixed effects of treatment and group. Increased BW compared to CON was observed days -29, -13, and -1 in SCFP57 steers (P ≤ 0.05), with SCFP29 being intermediate days -13 and -1. Overall G:F was improved in SCFP29 and SCFP57 (P = 0.01). On day -29, FRAP was greater in SCFP57 than CON (P = 0.02). The percent of gamma delta T cells and natural killer cells in both SCFP29 and SCFP57 was greater than CON on day -13 (P = 0.02). There were no treatment × day effects for muscle gene expression measured (P ≥ 0.25). Interleukin 6 tended to decrease in SCFP29 and SCFP57 on day -13 (P = 0.10). No other treatment effects were observed for muscle gene expression. Muscle gene expression of interleukin 15 was increased (P = 0.01), and expression of interleukin 8 was decreased (P = 0.03) due to RAC feeding. Increased growth in SCFP-fed cattle may be related to changes in anti-oxidant capacity and the immune system.

Saccharomyces cerevisiae fermentation products (SCFP) can provide additional support for improved growth performance. This study investigated the effects of supplementing a SCFP (NaturSafe; Diamond V, Cedar Rapids, IA; 12 g per steer per d) for 29 (SCFP29) or 57 (SCFP57) d before harvest when also feeding ractopamine hydrochloride (RAC; 300 mg per steer per d; Optaflexx, Elanco Animal Health, Greenfield, IN) for 29 d before harvest. Compared to steers not fed SCFP (CON), SCFP29 and SCFP57 had improved gain:feed for the entire feeding period. Steers supplemented with SCFP had increased percentages of gamma delta T cells and natural killer cells 13 d before harvest compared to CON. Gene expression of cytokine and anti-oxidant signaling in muscle were changed in all treatments during RAC compared to before RAC. Improvements in growth during RAC with SCFP supplementation may be due to the changes in anti-oxidant and cytokine signaling in muscle.