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• Repeated ACTH injections decreased plasma Zn concentrations in lambs receiving supplemental Zn, to concentrations considered to be marginally deficient. • Fiber digestion was negatively affected by supplemental Zn from ZnSO4. • Fecal Zn tended to increase due to ACTH in lambs fed supplemental Zn. • Trace mineral apparent absorption, and nutrient digestibility were not affected by ACTH injection administration. The objective was to evaluate the effects of Zn supplementation and adrenocorticotropic hormone (ACTH) injections on nutrient digestibility, trace mineral metabolism and status. It was hypothesized that ACTH would decrease nutrient digestibility and Zn retention, but Zn supplementation would improve Zn retention, regardless of ACTH administration. Twenty-two Polypay cross weathers previously enrolled in a trial, consumed a moderately Zn deplete diet (22 mg Zn/kg DM) for 52 d, followed by being housed in metabolism crates for 15 d while receiving one of two diets: CON (Zn deplete diet) or ZINC (CON plus 40 mg Zn/d from ZnSO 4). Lambs rested for one day outside of crates then returned to crates for this 5 d study. Lambs continued to receive dietary Zn treatments and were randomly assigned to receive injectable treatments, once daily on d 1–4 at feeding: SALINE (2 mL saline I.M.), STRESS (80 I.U. ACTH I.M.); lamb was experimental unit (n = 5–6/treatment) in a 2 × 2 factorial design. Total fecal and urine collection was conducted on d 3–5, and blood samples were collected on d 0, 1, and 4, 3 h post feeding. Day 4 plasma Zn concentrations, covariate adjusted with d 0 concentrations, displayed a diet × injection tendency (P = 0.06) where ACTH given to ZINC lambs depressed plasma Zn to values similar to CON lambs. Day 1 and 4 cortisol concentrations determined 3 h after injection administration were increased in STRESS vs. SALINE (P < 0.01). Day 4 plasma Cu concentrations, covariate adjusted with d 0 concentrations were lesser in STRESS vs. SALINE (P = 0.04). Day 4 plasma Fe concentrations were unaffected by diet or injection treatment (P ≥ 0.18). Apparent absorption of Zn was increased (P < 0.01) in CON vs. ZINC, but were similar in STRESS vs. SALINE (P = 0.13). Zinc retention, and apparent absorption of Mn and Cu was similar across treatments (P ≥ 0.19). Organic matter (OM) digestibility tended to be decreased in ZINC vs. SALINE (P = 0.07); neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility were decreased (P ≤ 0.04) in ZINC vs. SALINE. Injection treatment had no effect on macronutrient digestibility (P ≥ 0.37). The CON lambs were marginally Zn deficient based on plasma Zn concentrations and rate of apparent absorption, while fiber digestion was impaired by Zn supplementation. Plasma cortisol concentrations indicate lambs receiving ACTH experienced physiological stress, however this had limited effects on macro or micronutrient metabolism. [ABSTRACT FROM AUTHOR]

Competing Interests: The authors declare that they have no conflicts of interest relevant to the content of this article.

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., (© 2024. The Author(s).)

Chelated copper ( Cu ) sources, such as Cu glycinate ( CuGly ), may be more bioavailable relative to Cu sulfate ( CuSO 4 ) when fed to ruminants under antagonistic pressure. The objective of this study was to determine the bioavailability of CuGly (GemStone Cu; Phibro Animal Health) relative to CuSO 4 in steers fed a diet supplemented with 0.3% sulfur and 2 mg molybdenum/kg of dry matter ( DM ). Sixty Angus crossbred steers ( n  = 12 per treatment) averaging 288 ± 4.85 kg were enrolled in a 90-d study and fed a corn silage-based diet with one of five Cu supplementation strategies, including no supplemental Cu (CON ), 5 or 10 mg supplemental Cu from CuSO 4 /kg DM, and 5 or 10 mg supplemental Cu from CuGly/kg DM. Steers were housed in pens equipped with GrowSafe feed bunks (GrowSafe Systems Ltd., Airdire, AB, Canada), with six steers per pen. Growth performance, liver Cu, and plasma Cu were analyzed in the MIXED procedure of SAS 9.4 (SAS Inst. Inc, Cary, NC) with orthogonal contrasts to compare CON vs. 5 mg Cu/kg DM, CON vs. 10 mg Cu/kg DM, 5 vs. 10 mg Cu/kg DM, and CuSO 4 vs. CuGly. Copper indices were regressed against Cu intake and slopes were calculated using the GLM procedure SAS. Dietary Cu supplementation did not affect steer body weights on days 0, 28, 56, or 90 ( P  ≥ 0.52), average daily gain, dry matter intake, or gain:feed ( P  ≥ 0.36). Final plasma Cu concentration did not differ between CON vs. 5 mg Cu/kg DM ( P  = 0.79), CON vs. 10 mg Cu/kg DM ( P  = 0.65), or 5 vs. 10 mg Cu/kg DM ( P  = 0.39). Steers receiving CuSO 4 tended to have greater final plasma Cu concentrations than those receiving CuGly ( P  = 0.08). Initial liver Cu concentration averaged 374 mg Cu/kg DM, which is considered highly adequate. No steers reached deficient Cu status by the end of the 90-d period. Control steers had lesser final liver Cu concentrations than supplemented steers ( P  ≤ 0.04). Steers receiving 10 mg supplemental Cu/kg DM had greater liver Cu concentrations than those receiving 5 mg supplemental Cu/kg DM ( P  = 0.01). Copper source had no effect on final liver Cu concentrations ( P  = 0.57) and based on liver Cu and Cu intake the bioavailability of CuGly was similar to CuSO 4 (115%; P  = 0.27). The initially high Cu status and the fact that cattle did not become Cu deficient may have impacted the relative bioavailability results, and more research is needed to investigate the role initial Cu status and antagonistic pressure play in the bioavailability of chelated Cu sources., Competing Interests: None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

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., (© 2024. The Author(s).)

Angus-cross steers (n = 144; 362 kg ± 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., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The effects of supplemental Zn within steroidal implant strategy on performance, carcass characteristics, trace mineral status, and muscle gene expression were tested in a 59-d study using 128 Angus-crossbred steers (492 ± 29 kg) in a 2 × 4 complete randomized design. Implant strategies included no implant (NoIMP) or Component TE-200 (TE200; Elanco, Greenfield, IN) administered on day 0. Zinc was supplemented at 0, 30, 100, or 150 mg Zn/kg dry matter (Zn0, Zn30, Zn100, Zn150, respectively) from ZnSO4. Steers were stratified by body weight (BW) to pens (n = 5 or 6 steers/pen) equipped with GrowSafe bunks (GrowSafe Systems Ltd., Airdrie, AB, Canada) and assigned treatments (n = 15, 16, or 17 steers/treatment). Cattle were weighed on days -1, 0, 18, and 59 with blood collected on days -1, 18, 40, and 59. Muscle samples were collected from the longissimus thoracis on day 11 and liver samples were collected on day 55 or 56. Data were analyzed using the Mixed Procedure of SAS via contrast statements testing the linear and quadratic response to Zn supplementation within implant treatment and NoIMP vs. TE200 for performance, carcass, blood, and liver parameters. Specific contrast statements were formed for the analysis of gene expression in muscle including: Zn0 vs. Zn150 within NoIMP and TE200, NoIMP vs. TE200 (Zn0 and Zn150 only), and the linear effect of supplementing Zn0, Zn100, and Zn150 within TE200. Steer was the experimental unit. Day 18 BW and days 0 to 18 average daily gain (ADG) were linearly increased due to Zn supplementation within TE200 (P ≤ 0.002) in conjunction with a linear increase from Zn in day 11 muscle epidermal growth factor receptor, matrix metalloproteinase 2, and phosphodiesterase 4B gene expression of TE200 steers (P ≤ 0.05). Plasma Zn on days 18 and 40 linearly increased with increasing Zn supplementation regardless of implant treatment (P ≤ 0.03) and was lesser for TE200 than NoIMP steers on day 18 (P = 0.001). Day 59 BW and hot carcass weight (HCW) were greater for TE200 vs. NoIMP (P ≤ 0.002) and HCW of implanted steers tended to linearly increase with increasing Zn supplementation (P = 0.09). No effects of Zn supplementation were observed in NoIMP for HCW, BW, or ADG (P ≥ 0.17). Yield grade and 12th rib fat tended to quadratically decrease within NoIMP (P ≤ 0.09), with Zn100 being the most lean. These data indicate increasing supplemental Zn influences steroidal implant signaling machinery while increasing the Zn status and implant-induced growth of feedlot cattle., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Angus-cross steers (n = 144; 359 kg ± 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., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

It was hypothesized that the longissimus thoracis (LT) muscle proteome, phosphoproteome, and metabolome could explain postmortem metabolism and tenderness differences in muscle from cattle supplemented zinc (Zn) and/or ractopamine hydrochloride (RH). High percentage Angus steers (N = 20) were fed in a 2 × 2 factorial assigned to Zn and RH treatments: control (CON; n = 10; analyzed 36 mg Zn/kg dry matter [DM]) or supranutritional Zn supplementation (SUPZN; n = 10; control diet + 60 mg Zn/kg DM [from ZnSO4] + 60 mg Zn/kg DM [from Zn-amino acid complex]) for the entire 89-d trial. During the 28 d before harvest, steers were blocked by body weight within Zn treatments to RH treatments of 0 (NO; n = 10) or 300 mg (RAC; n = 10) per steer per day. Steers were harvested at the Iowa State Meat Laboratory, where pH decline (1, 3, 6, and 24 h postmortem) was measured. At 24 h postmortem, LT muscle sections were removed from carcasses, and steaks were analyzed for Warner-Bratzler shear force (WBSF) values at 1, 3, 7, and 14 d postmortem. Muscle samples were taken at 1 h, 1, 3, 7, and 14 d postmortem for the following analysis: troponin-T degradation (1, 3, 7, and 14 d postmortem), myosin heavy chain analysis (1 h postmortem), sarcoplasmic proteome analysis through tandem mass tagging analysis (1 h and 1 d postmortem), metabolome analysis (1 h and 1 d postmortem), and phosphoproteome analysis (1 h postmortem). SUPZN-NO tended to have a lower (P = 0.06) pH at 6 h postmortem and a lower WBSF value (P = 0.06) at 1 d postmortem. CON-RAC had a higher (P = 0.04) pH at 6 h postmortem and WBSF value (P < 0.01) at 1 d postmortem. A lower pH at 6 h postmortem and lower WBSF value at 1 d postmortem in the SUPZN-NO treatment was accompanied by more sorbitol and fructose at 1 d postmortem, and less myosin regulatory light chain 2 at 1 h postmortem, and less adenosine monophosphate deaminase 1 (AMPD1) at 1 d postmortem than all other treatments. A higher pH at 6 h postmortem and higher WBSF value at 1 d postmortem in CON-RAC and SUPZN-RAC was accompanied by more soluble structural proteins (troponin-T and myosin-7) at 1 h postmortem than CON-NO. At 1 h postmortem, CON-RAC had more glyceraldehyde-3-phosphate dehydrogenase than CON-NO or SUPZN-RAC. Differences in energy metabolism enzymes, metabolites, and structural proteins may affect ATP production, rigor development, and lactate buildup which may explain the differences in postmortem metabolism and tenderness development at 1 d postmortem., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The study's aim was to evaluate the effect of dietary Zn supplementation on steer performance, biomarkers of inflammation and metabolism, and liver abscess formation in response to a mild acidosis challenge. Forty-two steers (417 ± 3.99 kg; n = 6/pen) were housed in pens with bunks designed to measure individual dry matter intake ( DMI ) and fed one of two diets containing either 0 (CON; n = 18) or 90 mg Zn/kg from a Zn-amino acid complex ( Zn-AA ; n = 18; AvailaZn; Zinpro) for 109 d. Six additional steers were fed the CON diet and did not undergo the acidosis challenge ( NON ; n = 6). The acidosis challenge included restricting steers to 50% of the previous 7 d daily DMI on days 46 and 47, steers were individually provided 10% of DMI as cracked corn (as-fed) at 0800 h followed by ad libitum feed access 2 h post-grain consumption. Steer was the experimental unit, and two contrasts were constructed: NON vs. CON and CON vs. Zn-AA. Blood samples were collected on days 40, 48, 53, 69, 80, and 108 and analyzed as repeated measures. Final body weight and overall average daily gain (2.29, 2.30, and 2.31 ± 0.920 kg/d for CON, Zn-AA, and NON, respectively) were not different ( P ≥ 0.74) between treatments. By design, DMI was greater ( P < 0.01) for NON compared to CON on day 46 but was not different ( P ≥ 0.41) for the rest of the experiment. While hot carcass weight (423, 428, and 424 ± 7.9 kg for CON, Zn-AA, and NON, respectively) and ribeye area were not different ( P ≥ 0.53) due to treatment, marbling score tended ( P = 0.06) to be greater in CON compared to Zn-AA. The 12th rib backfat thickness was greater ( P = 0.05) in NON vs. CON steers. Liver abscess incidence tended to be greater ( P = 0.12) in CON (24% abscesses) vs. Zn-AA (6% abscesses). NON had a greater incidence ( P = 0.05; 50% abscesses) compared to CON. Overall, blood fibrinogen and leukocyte counts were not different between treatments ( P ≥ 0.67); however, neutrophil-to-lymphocyte ratio tended to be greater in NON vs. CON ( P = 0.08). Serum aspartate aminotransferase and gamma-glutamyl transferase concentrations were greater in NON vs. CON ( P ≤ 0.02), and serum alkaline phosphatase concentration was lesser in CON vs. Zn-AA ( P < 0.01). Overall, dietary Zn supplementation tended to lessen incidence of liver abscesses with limited impacts on overall cattle performance. Shifts in liver enzymes may represent opportunities to identify cattle with liver abscesses earlier in the feeding period., Competing Interests: Lundy-Woolfolk, Genther-Schroeder, and Hansen declare no conflicts of interest. Branine is an employee of Zinpro Corp. and reviewed the manuscript but offered only grammatical suggestions for improvement. The content was at the discretion of the Iowa State University researchers., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)

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., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Low-risk, weaned Angus-crossbred steers (n = 72; 284 ± 25 kg) were used in a 42-d receiving study. Steers were housed in pens (n = 6 steers per pen) equipped with GrowSafe bunks for determination of individual animal feed disappearance. Dietary treatments (n = 24 steers per treatment) included: 1) trace minerals (TM) from an organic source (Availa4; Zinpro Corp., Eden Prairie, MN) at 7 g·steer-1·d-1; for 42 d (ORG); 2) ORG for entire 42-d plus AvailaZn (Zn amino acid complex, Zinpro Corp., Eden Prairie, MN) to provide 1,000 mg Zn·steer-1·d-1 for first 14 d (ORG+Z); 3) inorganic TM sources to supplemented at equivalent concentration as in ORG for 42-d (ING). Cattle were weighed on day -1, 0, 14, 41, and 42. Whole blood was collected (n = 72 steers) on day 0, 14, and 42. Liver biopsies were conducted (n = 36 steers; 3 steers per pen) on day 0, 14, and 42. Flow cytometry measures were conducted using whole blood on day 1, 14, and 42 for determination of circulating frequencies of immune cell populations. There was a tendency for improved overall average daily gain (P = 0.07) where both ORG and ORG+Z were greater than ING. Final body weight did not differ (P = 0.21) and overall dry matter intake was unaffected by dietary treatment (P ≥ 0.18). However, overall gain-to-feed ratio was improved (P = 0.01) in steers supplemented organic TM (ORG and ORG+Z) compared to ING. Plasma Zn concentration did not differ at any time point during the study (P ≥ 0.20). Liver Zn concentration did not differ between treatments on day 0 or 42; however, on day 14 ING tended (P = 0.09) to be greater than ORG+Z with ORG being intermediate. Plasma Cu was unaffected by dietary treatment (P ≥ 0.34) on day 0, 14, and 42. Plasma Fe did not differ on day 0 or 42 but tended to be greater in ORG and ORG+Z compared to ING (P = 0.08) on day 14. Dietary treatment did not alter (P ≥ 0.22) liver Fe or Mn concentration at any time point. Frequency of total circulating natural killer (NK) and CD8 T cells measured on day 0, 14, and 42 did not differ (P ≥ 0.07). However, cell surface markers of activation (CD16, CD44, and CD8) on NK cells measured on day 14 did differ because of treatment (P ≤ 0.05). Results presented herein indicate TM from an organic source supplemented to steers during receiving can positively influence growth rate and feed efficiency. Regardless of source, TM supplementation affected markers of immune function but did not influence the prevalence of circulating NK and CD8 T-cell populations., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)

This study investigated the effects of injectable vitamin C (VC) at weaning and prior to transit on growth performance and immune function in early-weaned beef steers. On day 0, 91 Angus × Simmental steers (92 ± 4 kg) were weaned (65 ± 11 d of age), given vaccination boosters, blocked by age, and randomly assigned to weaning (WEAN) treatments: intramuscular injections (20 mL per steer) of VC (250-mg sodium ascorbate per mL; 5 g per steer) or saline (SAL). From days 0 to 48, steers were housed at the Dixon Springs Agricultural Center (Simpson, IL) in pens (six pens; N = 14 to 16 steers per pen) equipped with two to three Vytelle bunks to measure individual daily feed disappearance. On day 49, half of the steers in each WEAN treatment were randomly assigned to an additional injection treatment (20 mL per steer) of VC or SAL prior to transport (TRANS). After administering pretransit injections, all steers were loaded onto a commercial livestock trailer with equal representation of treatments across compartments. Steers were transported for 6 h (approximately 480 km) to the Illinois Beef and Sheep Field Laboratory (Urbana, IL). Upon arrival, steers were sorted into pens (six pens; N = 13 to 17 steers per pen) with 2 Vytelle bunks per pen. Steers were weighed on days 0, 1, 14, 48, 49, 64, 78, 106, and 107. Blood was collected (WEAN = 24 steers per treatment; TRANS = 12 steers per treatment) on days 0, 1, 2, 14, 49 (pre- and posttransit), 50, and 51. Data were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of age block, WEAN, TRANS, and WEAN × TRANS. Plasma ascorbate concentrations were greater (WEAN × time P < 0.01) on days 1 and 2 for steers that received VC at weaning. Similarly, for steers that received VC on day 49 pretransit, ascorbate concentrations were greater (TRANS × time P = 0.04) on days 49 posttransit, 50, and 51. Treatments did not affect (P ≥ 0.13) body weight, average daily gain, or gain to feed throughout the trial. Serum Bovine Viral Diarrhea Virus type 1 and 2 antibody titers on days 14 and 51 were not affected (P ≥ 0.32) by treatment. Injectable VC administered to early-weaned beef steers at the time of weaning or pretransit increased plasma ascorbate concentrations but did not improve growth performance or antibody response to vaccination booster., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The objective was to determine the effects of injectable vitamin E (VE) before or after transit on feedlot cattle receiving performance, health, and blood parameters. Angus × Simmental steers (n = 196; body weight [BW] = 163 ± 29 kg) were utilized in a randomized complete block design. Steers were blocked by BW and randomly assigned to 1 of 3 treatments: intramuscular injections of saline pre- and post-transit (CON), intramuscular injections of VE (2,000 mg d-α-tocopherol) pre-transit and saline post-transit (PRE), or intramuscular injections of saline pre-transit and VE (2,000 mg d-α-tocopherol) post-transit (POST). Pre-transit injections were administered on day 0, and steers were transported on day 7 for approximately 4 h (348 km). After arrival, steers were fed a common corn silage-based diet in GrowSafe bunks. Final BW tended to be greater (P = 0.08) for CON steers compared with POST steers while PRE steers were intermediate. From days 7 to 63, treatment affected average daily gain (ADG) with PRE and CON steers exhibiting (P = 0.04) greater ADG compared with POST steers. Dry matter intake (DMI), water intake, and gain to feed from days 7 to 63 were not affected (P ≥ 0.17) by treatment. Day 0 serum α-tocopherol concentrations were considered marginal (2.3 ± 0.2 mg/l). A treatment × day interaction (P < 0.01) was observed for serum α-tocopherol concentrations. Serum α-tocopherol concentrations were greatest for PRE steers on day 7 (prior to and post-transit), but greater for POST steers on dys 10 and 14. Plasma ferric-reducing antioxidant potential concentrations increased (P = 0.04) for POST steers compared with CON steers and PRE steers being intermediate. Plasma non-esterified fatty acids (NEFA) concentrations exhibited a treatment × day interaction (P = 0.04) with CON and POST steers being 16% and 14% greater than PRE steers on day 14, respectively. On day 21, NEFA concentrations were greatest for POST steers compared with PRE steers and CON steers being intermediate. There was no main effect (P ≥ 0.14) of treatment on the number of bovine respiratory disease morbidity treatments. Hair cortisol concentrations were decreased (P < 0.01) 14 days after transit for PRE and POST steers compared with CON steers. Overall, injectable VE administered before or after transit increased serum tocopherol concentrations while reducing stress, but did not improve the growth performance of beef steers during the receiving phase., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Fifty-four Angus-cross steers (297 kg ± 12) were stratified by body weight (BW) to pens (six steers per pen) to determine the effects of supplemental Zn on posttransit growth performance and blood and muscle metabolites. Dietary treatments started 25 d before trucking: control (CON; analyzed 54 mg Zn/kg DM), industry (IND; CON + 70 mg supplemental Zn/kg DM), and supranutritional Zn (SUPZN; CON + 120 mg supplemental Zn/kg DM). Supplemental Zn was bis-glycinate bound Zn (Plexomin Zn; Phytobiotics North America, Cary, NC). On day 0, steers were loaded onto a commercial trailer and transported in 18 h (1,822 km). Individual BW was recorded on days -26, -25, -1, and 0 (pre-transit), 1 (posttransit), 6, 27, and 28. Blood was collected on days -1, 1, 6, and 27. Longissimus thoracis biopsies were collected on days -1, 1, and 28. Daily individual feed disappearance was recorded via GrowSafe bunks. Data were analyzed using Proc Mixed of SAS with fixed effect of diet and steer as the experimental unit (growth performance, blood: n = 18 steers per treatment; muscle: n = 12 steers per treatment). Individual initial BW was used as a covariate in BW analysis. Contrast statements to test linear, quadratic, and Zn effects were used to analyze performance and blood parameters. Repeated measures analysis was used for posttransit DMI recovery and weekly posttransit DMI and Zn intake with the repeated effect of time. MetaboAnalyst 5.0 was utilized for statistical analysis of day 1 (off truck) muscle metabolites. Plasma Zn linearly increased due to Zn on days 1, 6, and 27 (P = 0.01), and off-truck (day 1) serum lactate increased over day -1 by 20%, 0%, and 20% in CON, IND, and SUPZN, respectively (Quadratic: P = 0.01). Muscle lactate tended to increase posttransit in CON and IND (P ≤ 0.07) but not SUPZN. Muscle metabolites relating to amino acid and nitrogen metabolism were increased in all treatments posttransit (P ≤ 0.02), and alanine-glucose cycle metabolites tended to increase in CON and IND (P ≤ 0.07). Steers supplemented with Zn recovered pretransit DMI quicker than CON (by d 2: P = 0.01), while IND had greater overall posttransit DMI than CON with SUPZN intermediate (P = 0.04), and Zn-fed steers had greater ADG posttransit (P = 0.04). Zinc supplementation mitigated muscle or serum lactate increases due to transit and increased posttransit ADG., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The objectives were to assess the effects of dietary Sweet Bran (Cargill Corn Milling, Blair, NE) on performance and feeding behavior of feedlot steers and determine if terminal implant pen sorting affects performance, feeding behavior, and liver abscess (LA) rate. Two hundred sixteen Angus-cross steers (253 ± 18 kg) were stratified by body weight (BW) to 36 pens. From d 0 to 60, diets contained 40% Sweet Bran (SWBR) or 25% modified distiller's grains and 15% dry rolled corn (MOD; n = 18 pens/treatment). On d 60, steers began transition within treatments to finishing diets containing 25% Sweet Bran or 25% modified distiller's grains (MDGS). On d 111, half of the pens for each dietary treatment were re-stratified by BW to pens (SORT) while the other half were returned to original pens (NOSORT; n = 9 pens/treatment). Steer BW and pen dry matter intake (DMI) were recorded monthly. Rate of feed disappearance was determined on d 5/6, 53/54, 104/105, and 117/118. Pen was the experimental unit for all analyses. The model included the fixed effect of diet for all pre-sort analyses; post-sort analyses included the fixed effects of diet, sort, and the interaction and the random effects of pen and the interaction of diet and pen. On d 60, SWBR had greater BW than MOD ( P = 0.05), and SWBR had a greater average daily gain (ADG) from d 0 to 60 ( P = 0.05). Though there were no differences after d 28, SWBR had greater DMI d 0 to 28 ( P = 0.05). From d 60 to 88, SWBR tended to have lesser ADG than MOD ( P = 0.09). Post-sort (d 111 to 196), SWBR tended to have lesser ADG than MOD ( P = 0.06), and SORT had a greater rate of feed disappearance than NOSORT (d 117/118; P = 0.01); there were no differences on other dates (Diet: P ≥ 0.38). For final BW, there was a tendency for MOD to be greater than SWBR, and SORT tended to be greater than NOSORT (Diet: P = 0.06; Sort: P = 0.10). Pre- and post-sort ruminal pH had no treatment by day differences ( P ≥ 0.77). LA incidence averaged 25%, though rate was not affected by diet, sorting, or the interaction ( P ≥ 0.16). Overall, there were no dietary differences in feed disappearance rates, though SORT steers had greater rate of feed disappearance than NOSORT steers on d 117/118. Nominal differences in feeding behavior were noted and including Sweet Bran in the diet was beneficial in the growing period as cattle adjusted to the feedlot., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Ninety-two Angus-crossbred steers (424 ± 28.3 kg initial body weight) were used in a 98-d study to assess the effects of increasing Zn supplementation on cattle performance, liver and plasma trace mineral concentrations, blood metabolites, and carcass characteristics. All steers were implanted with a Component TE-200 (200 mg trenbolone acetate + 20 mg estradiol; Elanco Animal Health, Greenfield, IN) on d 0 and fed 300 mg‧steer -1 ‧d -1 of ractopamine hydrochloride (Zoetis, Parsippany, NJ) from d 70 to 98. Cattle were fed via GrowSafe bunks (GrowSafe Systems Ltd., Airdrie, AB, Canada), and steer served as the experimental unit ( n  = 22 or 23 steers/treatment). Supplemental Zn was administered through the diet at 0, 100, 150, or 180 mg Zn/kg on a dry matter basis from ZnSO 4 (Zn0, Zn100, Zn150, or Zn180, respectively). Cattle were weighed on d -1, 0, 9/10, 20, 41, 59, 69, 70, 78/79, 97, and 98. Blood was collected on d 0, 9/10, 69, 78/79, and 97, and liver biopsies on d 9/10 and 78/79 ( n  = 12 steers/treatment). Data were analyzed as a complete randomized design. Contrast statements were formed to test the linear, quadratic, and cubic effects of Zn supplementation and test Zn0 vs. Zn supplementation. Day 10 and 70 body weight (BW) and d 0 to 10 and 0 to 70 average daily gain were linearly increased with Zn supplementation ( P  ≤ 0.05), and greater for Zn supplemented steers ( P  ≤ 0.03). No effects of Zn supplementation were observed on final BW, dressing percentage, ribeye area, 12th rib fat, or marbling ( P  ≥ 0.11). Hot carcass weight tended to be 7 kg greater for Zn supplemented steers than Zn0 ( P  = 0.07), and yield grade linearly increased with increasing Zn supplementation ( P  = 0.02). Day 10 liver Mn concentrations tended to quadratically decrease ( P  = 0.08) with increasing Zn supplementation, though d 79 liver Mn concentrations and arginase activity were not influenced by Zn ( P  ≥ 0.28). Day 10 liver arginase activity tended to be ( r  = 0.27; P  = 0.07) and d 10 serum urea nitrogen was correlated with d 10 liver Mn ( r  = 0.55; P  < 0.0001). Zinc supplementation linearly increased d 10 liver Zn and d 10, 69, 79, and 97 plasma Zn concentrations ( P  ≤ 0.05). A cubic effect of Zn was observed on d 79 liver Zn ( P  = 0.01) with lesser liver Zn in Zn0 and Zn150 steers. These data suggest increasing dietary Zn improves growth directly following the administration of a steroidal implant and that steroidal implants and beta agonists differ in their effects on protein metabolism., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

This study examined the effects of injectable vitamin C (VC) before transport and duration of transit on feedlot performance, inflammation, and muscle fatigue in cattle. One hundred thirty-two Angus-cross steers (393 ± 4 kg) were stratified by body weight (BW) to a 2 × 2 factorial of intramuscular injection (INJ; 20 mL/steer): VC (250 mg sodium ascorbate/mL) or saline (SAL) and road transit duration (DUR): 18 h (18-h; 1,770 km) or 8 h (8-h; 727 km). On day 0, steers were weighed and given INJ of VC or SAL immediately before transport. Upon return (day 1), BW and blood were collected before steers returned to pens equipped with GrowSafe bunks. Steers were weighed on days 0, 1, 7, 15, 30, 31, 54, and 55. Data were analyzed via ProcMixed of SAS (experimental unit = steer; 32 to 34 steers/treatment) with fixed effects of INJ, DUR, and the interaction. Blood was collected on days -5, 1, 2, 3, and 7 (n = 9 steers/treatment); blood parameters were analyzed as repeated measures with the repeated effect of day. Area under the curve (AUC) for plasma ferric reducing antioxidant power (FRAP) was calculated using R. Final BW was greater for 8 h compared to 18 h (P = 0.05) with no effect of INJ or interaction (P ≥ 0.51). Dry matter intake (DMI) from days 1 to 7 was greater for VC-8, intermediate for VC-18 and SAL-18, and least for SAL-8 (P = 0.02). Overall, DMI tended to be greatest for SAL-18, intermediate for VC-18 and VC-8, and least for SAL-8 (P = 0.08). Days 7 to 31 gain:feed (G:F) was greatest for VC-18 compared to other treatments (INJ × DUR, P = 0.05), and there was no effect of treatment on overall G:F (P ≥ 0. 19). There was no INJ or INJ × DAY (P ≥ 0.17) effect on serum lactate, haptoglobin, or non-esterified fatty acid. However, these blood parameters were greater on day 1 for 18 h compared to 8 h, and both treatments returned to near baseline by day 3 (DUR × DAY, P < 0.01). Plasma ascorbate concentrations on day 1 were greater for VC compared to SAL and returned to baseline by day 2 (INJ × DAY, P < 0.01). Plasma FRAP AUC from days -5 to 3 was greatest for VC-18, intermediate for VC-8 and SAL-8, and least for SAL-18 (INJ × DAY, P = 0.02). This suggests an antioxidant prior to long-haul transit positively influenced antioxidant capacity; however, VC did not improve overall post-transit performance. Although longer transit duration increased indicators of muscle fatigue and inflammation, post-transit performance was not appreciably different between transit durations., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Seventy-two Angus-crossbred steers (411 ± 16 kg) were assigned to a 2 × 3 factorial arrangement of treatments to examine the effects of blended Zn source supplementation on performance, carcass characteristics, and trace mineral parameters of steers administered no implant or a two-implant program. Factors included implant (IMP) strategies and Zn supplementation. During the 126-d study, steers were either not implanted (NoIMP) or implanted (IS/200; Elanco, Greenfield, IN) on days 0 (Component TE-IS; 80 mg trenbolone acetate + 16 mg estradiol) and 57 (Component TE-200; 200 mg trenbolone acetate + 20 mg estradiol). All steers were fed 70 mg Zn/kg on a dry matter (DM) basis from ZnSO 4 + 30 mg Zn/kg DM from either basic ZnCl (Vistore Zn, Phibro Animal Health, Teaneck, NJ), Zn glycinate (Gemstone Zn, Phibro Animal Health), or ZnSO 4 (ZnB, ZnG, or ZnS, respectively). Steers were blocked by weight into pens of 6 and fed a dry rolled corn-based diet via GrowSafe bunks (GrowSafe Systems Ltd.; Airdrie, AB, Canada). Data were analyzed using the Mixed Procedure of SAS, with fixed effects of Zn, IMP, and the interaction. Steer was the experimental unit ( n = 12 steers/treatment). Liver and muscle collected on days -5, 14, 71, and 120 were analyzed for Zn concentration, and data were analyzed as repeated measures (repeated effect = Day). An IMP × Zn tendency ( P = 0.07) was observed for day 126 body weight with no effects of Zn within NoIMP, whereas ZnS tended to be heavier than ZnB with ZnG intermediate within IS/200. Carcass-adjusted overall feed efficiency (G:F) was greatest for ZnS (Zn; P = 0.02). Implanted cattle had greater DM intake, G:F, and carcass-adjusted performance ( P ≤ 0.01). Liver Zn concentrations were greater for IS/200 by day 120 (IMP × Day; P = 0.02). Within IS/200, ZnG tended to have greater muscle Zn than ZnS, whereas ZnB was intermediate (Zn × IMP; P = 0.09). No Zn or IMP × Zn ( P ≥ 0.12) effects were observed for carcass data. However, IS/200 had greater hot carcass weight, dressing percentage, and ribeye area than NoIMP ( P ≤ 0.001). These data suggest that implants improve growth and influence Zn metabolism. Future work should examine Zn sources and supplementation alongside implant strategies., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.)

To assess the efficacy of bis-glycinate bound Zn, 36 crossbred wethers (34 ± 2 kg) were sorted by body weight into three groups and stagger started on a Zn-deficient diet (18 mg Zn/kg dry matter [DM]; 22.5% neutral detergent fiber [NDF]) for 45 d prior to a 15-d metabolism period (10 d adaptation and 5 d collection). On day 46, lambs were randomly assigned to dietary treatments (four lambs treatment-1group-1): no supplemental Zn (CON) or 15 mg supplemental Zn/kg DM (ZINC) as Zn sulfate (ZS) or bis-glycinate (GLY; Plexomin Zn, Phytobiotics). Blood was collected from all lambs on days 1, 44, 56, and 61. Liver, jejunum, and longissimus dorsi samples were collected after euthanasia on day 61. Gene expression was determined via quantitative real-time polymerase chain reaction. Data were analyzed using ProcMixed of SAS (experimental unit = lamb; fixed effects = treatment, group, and breed) and contrast statements assessed the effects of supplemental Zn concentration (ZINC vs. CON) and source (GLY vs. ZS). After 15 d of Zn supplementation, plasma Zn concentrations were greater for ZINC vs. CON and GLY vs. ZS (P ≤ 0.01); tissue Zn concentrations were unaffected (P ≥ 0.27). Liver Cu concentrations were lesser for ZINC vs. CON (P = 0.03). Longissimus dorsi Mn concentrations were greater for ZINC vs. CON (P = 0.05) and tended to be lesser for GLY vs. ZS (P = 0.09). Digestibility of DM, organic matter (OM), and NDF was lesser for ZINC vs. CON (P ≤ 0.05); acid detergent fiber digestibility tended to be greater for GLY vs. ZS (P = 0.06). Nitrogen retention (g/d) tended to be greater for GLY vs. ZS (P = 0.10), and N apparent absorption was lesser for ZINC vs. CON (P = 0.02). Zinc intake, fecal output, retention, and apparent absorption were greater for ZINC vs. CON (P ≤ 0.01). Apparent absorption of Zn was -5.1%, 12.8%, and 15.0% for CON, ZS, and GLY, respectively. Nitrogen and Zn retention and apparent absorption were not correlated for CON (P ≥ 0.14) but were positively correlated for ZINC (retention: P = 0.02, r = 0.52; apparent absorption: P < 0.01, r = 0.73). Intestinal expression of Zn transporter ZIP4 was lesser for ZINC vs. CON (P = 0.02). Liver expression of metallothionein-1 (MT1) tended to be greater for GLY vs. ZS (P = 0.07). Although Zn apparent absorption did not differ between sources (P = 0.71), differences in post-absorptive metabolism may be responsible for greater plasma Zn concentrations and liver MT1 expression for GLY-supplemented lambs, suggesting improved bioavailability of GLY relative to ZS., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Angus-crossbred steers ( n = 180; 292 ± 18 kg) from a single ranch were used to investigate the effects of a novel rumen-protected folic acid (RPFA) supplement on feedlot performance and carcass characteristics. On d 0, steers were blocked by body weight to pens (5 steers/pen), and pens within a block were randomly assigned to dietary treatments ( n = 6 pens/treatment): target intake of 0 (CON), 30 (RPFA-30), 60 (RPFA-60), 90 (RPFA-90), 120 (RPFA-120), or 150 (RPFA-150) mg RPFA·steer -1 ·d -1 . Steers were weighed before feeding on d -1, 0, 55, 56, 86, 87, 181, and 182. Pen average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F) were calculated for growing (d 0 to 56), dietary transition (d 56 to 87), finishing (d 87 to 182), and overall (d 0 to 182). Liver and blood samples were collected from two steers/pen before trial initiation and at the end of growing and finishing. Steers were slaughtered on d 183, and carcass data were collected after a 48-h chill. Data were analyzed as a randomized complete block design using ProcMixed of SAS 9.4 (fixed effects of treatment and block; experimental unit of pen). Liver abscess scores were analyzed using the Genmod Procedure of SAS 9.4. Contrast statements assessed the polynomial effects of RPFA. Supplemental RPFA linearly increased plasma folate at the end of growing and finishing ( P < 0.01), and linearly decreased plasma glucose at the end of growing ( P = 0.01). There was a cubic effect of RPFA on liver folate at the end of growing ( P = 0.01), driven by lesser concentrations for RPFA-30, RPFA-60, and RPFA-150. Growing period ADG and G:F were greatest for CON and RPFA-120 (cubic P ≤ 0.03). Transition period DMI was linearly increased due to RPFA ( P = 0.05). There was a tendency for a cubic effect of RPFA on the percentage of livers with no abscesses ( P = 0.06), driven by a greater percentage of non-abscessed livers in RPFA-30 and RPFA-60. Despite supplementing 1 mg Co/kg DM, and regardless of treatment, plasma vitamin B12 concentrations were low (<200 pg/mL), which may have influenced the response to RPFA as vitamin B12 is essential for recycling of folate., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Methane produced by cattle is one of the contributors of anthropogenic greenhouse gas. Methods to lessen methane emissions from cattle have been met with varying success; thus establishing consistent methods for decreasing methane production are imperative. Ferric iron may possibly act to decrease methane by acting as an alternative electron acceptor. The objective of this study was to assess the effect of ferric citrate on the rumen bacterial and archaeal communities and its impact on methane production. In this study, eight steers were used in a repeated Latin square design with 0, 250, 500 or 750 mg Fe/kg DM of ferric iron (as ferric citrate) in four different periods. Each period consisted of a 16 day adaptation period and 5 day sampling period. During each sampling period, methane production was measured, and rumen content was collected for bacterial and archaeal community analyses. Normally distributed data were analysed using a mixed model ANOVA using the GLIMMIX procedure of SAS, and non-normally distributed data were analysed in the same manner following ranking. Ferric citrate did not have any effect on bacterial community composition, methanogenic archaea nor methane production ( P >0.05). Ferric citrate may not be a viable option to observe a ruminal response for decreases in enteric methane production., Competing Interests: The authors declare that there are no conflicts of interest.

Background: Understanding the influence of dietary iron deficiency and dietary iron oversupplementation on intestinal health is important for both animal production and human health., Objective: The aim of this study was to determine whether dietary iron concentration influences intestinal physiology, morphology, and inflammation in the porcine duodenum., Methods: Twenty-four male pigs (21 d old) were fed diets containing either 20 mg Fe/kg [low dietary iron (L-Fe)], 120 mg Fe/kg [adequate dietary iron (A-Fe); control], or 520 mg Fe/kg [high dietary iron (H-Fe)] by FeSO4 supplement (dry matter basis). After 32-36 d, the duodenum was harvested from pigs and mounted in Ussing chambers for the measurement of transepithelial electrical resistance (TER), short-circuit current, and (3)H-mannitol permeability. Intestinal morphology and inflammation were assessed by histologic examination, and proinflammatory gene expression was assessed by real-time polymerase chain reaction., Results: Compared with A-Fe-fed pigs, pigs fed L-Fe diets exhibited reduced TER (by 30%; P < 0.05). Compared with that of A-Fe-fed controls, the paracellular flux of (3)H-mannitol across the duodenal mucosa was higher (P < 0.05) in L-Fe-fed (>100%) and H-Fe-fed (∼4-fold) pigs; the L-Fe-fed and H-Fe-fed groups did not differ significantly from one another. Compared with the L-Fe-fed pigs, the A-Fe-fed and H-Fe-fed pigs had malondialdehyde concentrations 1.4- and 2.5-fold higher in the duodenum and 4.4- and 6.6-fold higher in the liver, respectively (P < 0.05). Neutrophil counts were higher in both the L-Fe-fed (by 3-fold) and H-Fe-fed (by 3.3-fold) groups than in the A-Fe-fed group; the L-Fe-fed and H-Fe-fed groups did not significantly differ from one another. Duodenal mucosal tumor necrosis factor α (TNFA), interleukin (IL) 1β, and IL6 relative gene expression was upregulated by 36%, 28%, and 45%, respectively, in H-Fe pigs (P < 0.05), but not in L-Fe pigs, compared with A-Fe pigs., Conclusion: These data suggest that adequate but not oversupplementation of dietary iron in pigs is required to maintain intestinal barrier health and function., (© 2016 American Society for Nutrition.)

To investigate the effects of dietary iron (Fe) and age on Fe metabolism, we used 36 weaned barrows in a 2 x 3 design with 2 concentrations of dietary Fe [97 (control) and 797 (high Fe) mg Fe/kg dry matter] and 3 time points of tissue collection (after 21, 42, or 63 d on diets). Pigs were weighed and bled on d 0, 20, 41, and 62. High Fe reduced feed efficiency but did not affect pig weight gain. Blood hemoglobin concentrations and Fe concentrations of liver, intestine, and heart were increased by high dietary Fe on all days. Concentrations of liver and heart Fe increased with age. As determined by quantitative real-time PCR, hepatic expression of hepcidin (HAMP) in pigs given the high-Fe diet was 6.25-fold that of control pigs. In the intestine, relative mRNA levels of ferroportin, divalent metal transporter 1, and transferrin receptor were downregulated by high Fe. Expression of an alternative route of Fe absorption, solute carrier family 39 member 14 (SLC39A14), was downregulated in the intestine of pigs fed high dietary Fe. Additionally, duodenal mRNA level of certain genes including scavenger receptor class A, member 5, and frataxin decreased with age of the animal. Our findings indicate new roles in Fe metabolism for several mineral metabolism-associated genes and that some of these genes, such as SLC39A14, may be regulated in response to dietary Fe in pigs. Additionally, the expression of some genes examined in this study was affected by age, suggesting age dependency of Fe metabolism in pigs.

To investigate the effects of dietary iron (Fe) on manganese (Mn) metabolism, 24 weaned pigs (21 d old) were blocked by litter and weight and randomly assigned to the following treatments: 1) no supplemental Fe [low Fe (L-Fe)]; 2) 100 mg supplemental Fe/kg [adequate Fe (A-Fe)]; and 3) 500 mg supplemental Fe/kg [high Fe (H-Fe)]. The basal diet was analyzed to contain 20 mg Fe/kg. Tissues were harvested after 32 d of feeding. Daily gain (least square means +/- SEM) was greater in A-Fe pigs (328.3 +/- 29.9 g/d) than in L-Fe pigs (224.0 +/- 11.2 g/d). Hemoglobin concentrations on d 32 were lower in L-Fe pigs (62 +/- 3.5 g/L) than in A-Fe pigs (128 +/- 5.6 g/L) and did not differ between pigs fed A-Fe and H-Fe (133 +/- 12.0 g/L). Liver Fe increased with increasing dietary Fe. Relative hepatic hepcidin expression was greater in pigs fed A-Fe and H-Fe than in those fed L-Fe. Relative expressions of duodenal divalent metal transporter 1 (DMT1) and solute carrier family 39 member 14 (ZIP14) were increased in L-Fe pigs compared with H-Fe pigs. Liver copper (Cu) was higher in L-Fe (0.56 +/- 0.04 mmol/kg) and H-Fe (0.58 +/- 0.04 mmol/kg) pigs than in A-Fe pigs (0.40 +/- 0.04 mmol/kg). Liver Mn was lower in H-Fe pigs (0.15 +/- 0.01 mmol/kg) than in A-Fe (0.23 +/- 0.02 mmol/kg) or L-Fe pigs (0.20 +/- 0.02 mmol/kg). Duodenal Mn concentrations were greater in L-Fe pigs than in A-Fe or H-Fe pigs. Fe deficiency in pigs increased gene expression of duodenal metal transporters (DMT1 and ZIP14) and supplementation with H-Fe reduced expression of DMT1 and ZIP14, which may have decreased absorption of Mn.