Zinc supplementation strategies in feedlot heifers receiving an extended-release implant or an aggressive re-implant program

Determination of relative bioavailability of copper from copper glycinate in growing beef steers

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 CuSO4 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 CuSO4/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 CuSO4 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 CuSO4 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 CuSO4 (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.

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 ± 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 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 ± 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.

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

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 ZnSO₄ (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.

Effect of zinc source and implant strategy on performance, carcass characteristics, and trace mineral concentrations in finishing feedlot steers

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 ZnSO₄ + 30 mg Zn/kg DM from either basic ZnCl (Vistore Zn, Phibro Animal Health, Teaneck, NJ), Zn glycinate (Gemstone Zn, Phibro Animal Health), or ZnSO₄ (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.