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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. [ABSTRACT FROM AUTHOR]

To assess effects of a novel rumen-protected folic acid (RPFA) supplement, 180 Angus-cross steers (292 ± 18 kg) were blocked by body weight to pens and 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 on d -1, 0, 55, 56 (end of growing), 86, 87, 181, and 182. Liver and blood were collected (two steers/pen) before trial initiation and at the end of growing and finishing. Data were analyzed as a randomized complete block design using ProcMixed of SAS (fixed effects of treatment and block; experimental unit of pen). Liver abscess scores were analyzed using ProcGenmod of SAS. Contrast statements evaluated polynomial effects of RPFA and compared CON vs. RPFA-30. At end of growing, RPFA linearly increased plasma folic acid (P < 0.01) and linearly decreased plasma glucose (P = 0.01). Liver folic acid concentrations at end of growing were greatest for CON, RPFA-90, and RPFA-120 (cubic P = 0.01), and growing period (d 0 to 56) average daily gain and gain:feed were greatest for CON and RPFA-120 (cubic P ≤ 0.03). At end of finishing, RPFA linearly increased plasma folic acid concentrations (P < 0.01), and liver folic acid concentrations were lesser for CON vs. RPFA-30 (P = 0.04). Severe liver abscess percentage tended to be greater for CON vs. RPFA-30 (P = 0.09), while dressing percent was lesser for CON vs. RPFA-30 (P = 0.04). Overall (d 0 to 182) carcass-adjusted gain:feed tended to be greater for CON vs. RPFA-30 (P = 0.09). Although RPFA increased plasma folic acid concentrations throughout the study, feedlot performance was not improved, possibly due to low vitamin B12 status (plasma < 200 pg/mL) of steers, regardless of treatment. [ABSTRACT FROM AUTHOR]

One hundred twenty-eight Angus-cross steers (492 ± 29 kg) were utilized in a 2 × 4 factorial to determine the effects of dietary Zn within implant strategy on performance, carcass characteristics, and Zn status. Factors included Zn supplemented at 0, 30, 100, or 150 mg/kg dry matter ([DM]; Zn0, Zn30, Zn100, Zn150, respectively) from ZnSO4 and implant administered on d 0 as no implant (NoIMP) or Component TE-200 (TE-200; Elanco, Greenfield, IN). Cattle were stratified by bodyweight (BW) to GrowSafe equipped pens of 5 or 6 steers and assigned to pen-wide treatments (experimental unit of steer; n = 16/treatment). Steers were weighed on d -1, 0, 18, and 59 with blood collected on -1, 18, and 40. Via Proc Mixed of SAS, linear and quadratic effects of Zn within implant treatments and assessment of NoIMP vs. TE-200 were tested for performance, carcass characteristics, and plasma data, with initial value covariates. Plasma Zn concentrations on d 18 and 40 linearly increased within NoIMP and TE-200 (P ≤ 0.03) and were lesser for TE-200 than NoIMP on d 18 (P = 0.001). Zinc linearly increased (P ≤ 0.002) d 18 BW and d 0-18 average daily gain (ADG). Within TE-200, Zn increased dressing percentage (P = 0.01) and tended to increase hot carcass weight (P = 0.09) linearly. Carcass-adjusted final BW and overall ADG tended to increase (P = 0.10) linearly within TE-200, with no Zn effects within NoIMP (P ≥ 0.18). Implanting increased carcass-adjusted final BW 13 kg over NoIMP (P < 0.0001). Overall feed efficiency quadratically increased within NoIMP (P = 0.01) peaking at Zn100 with no observed Zn effects within NoIMP or TE-200 for overall DM intake (P ≥ 0.15). These data suggest implant-induced growth in steers may require dietary Zn above current national recommendations. [ABSTRACT FROM AUTHOR]

This study assessed the effect of Sweet BranTM (SWBR; 40% DM inclusion; Cargill Corn Milling, Blair, NE) or modified distiller's grains (MDGS; 25% DM inclusion) in the diet of newly received feedlot steers on feeding behavior and growing period performance. Diets were formulated for similar metabolizable protein and DM. Two hundred sixteen freshly weaned Angus-cross steers (253 kg ± 18.1) were stratified by BW to 36 pens (n = 18 per treatment; 6 steers/pen). Individual BW were recorded on d 0, 28, and 60. Eight pens per treatment were utilized to assess rate of feed disappearance early (day 5 and 6) and late (53 and 54) during growing by weighing feed in bunks every 2 hours post-delivery for 12 consecutive hours. Feed weights were averaged across consecutive days within pen and timepoint. Slopes were calculated between each timepoint to determine rate of feed disappearance. Data were analyzed with Proc Mixed of SAS 9.4; diet was fixed effect and pen was experimental unit. Feed disappearance slopes were analyzed as repeated measures with the repeated effect of time. Body weights did not differ on d 28 (P ≥ 0.29), but d 60 BW and d 0 to 60 ADG were greater for SWBR than MDGS (P < 0.05). Steers fed SWBR had greater DMI throughout the trial (P < 0.05). Feed efficiency (G:F) did not differ throughout the trial (P ≥ 0.31). Rate of feed disappearance on d 5/6 was greater for SWBR between hours 6-8, and greater for MDGS from hours 10-12. On d 53/54, SWBR had increased feeding rate during hours 0-2, while MDGS was increased from hours 8-10. Steers fed SWBR had a greater rate of feed disappearance earlier in the day and had improved DMI and growth than steers fed MDGS. [ABSTRACT FROM AUTHOR]

A 169-d study utilizing 208 Angus-cross heifers (291 ± 23 kg; 4 sources) in a 2×2 factorial examined the effects of implant strategy and Zn supplementation on growth and mineral status of heifers. Factors included 2 implant (Merck Animal Health, Madison, NJ) strategies: extended-release Revalor-XH on d 0 (REV-XH; 20 mg estradiol+200 mg trenbolone acetate) or Revalor-200 on d 0 and 91 (REV-200; 20 mg estradiol+200 mg trenbolone acetate) and 2 supplemental Zn (mg/kg dry matter [DM]; ZnSO4) strategies: national (30; NRC) or industry (100; IND) recommendations. Heifers were blocked by weight within source (n = 5 or 6 heifers/pen; 9 pens/treatment), received a corn silage-based diet (d 0-56), then transitioned to a corn-based diet fed via concrete bunks. Data were analyzed in Proc Mixed of SAS; fixed effects of implant (IMP), Zn, interaction, and source with the repeated effect of time for average daily gain (ADG) and liver mineral. Initial weight served as a covariate for performance and carcass data. Revalor-200 had greater ADG from d 0-28 and 91-120, while REV-XH peaked during d 56-91 (IMP × time; P = 0.02), corresponding to likely periods of greatest hormone payout from each implant. Liver Mn concentrations decreased on d 14 regardless of implant while d 105 and 164 concentrations were lesser for REV-200 (IMP × time; P = 0.02). Hot carcass weight, DM intake, carcass-adjusted ADG and feed efficiency were not different between IMP strategies (P = 0.18). Steers fed IND tended to be heavier on d 91 (P = 0.06) and were heavier on d 120 (P = 0.05) than NRC; however, final BW did not differ due to Zn (P = 0.37). The similar performance between implant strategies and superior performance during peak hormone payout by heifers supplemented IND vs. NRC suggests increased Zn may support rapid growth. [ABSTRACT FROM AUTHOR]