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.

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 supplemental Zn concentration and trace mineral source on immune function and associated biomarkers of immune status in weaned beef calves received into a feedlot.

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 receiving phase of the beef cattle production cycle occurs when calves are initially placed into the feedlot. During this time cattle are often exposed to stressors such as new environments, unfamiliar feedstuffs, and new pathogens. Together these stressors can result in lesser feed consumption. Along with lower total feed consumption, it is during this time that cattle likely require greater amounts of specific trace minerals (TM) to mount an effective immune response and maintain adequate growth. Therefore, this study aimed to evaluate the effects of supplemental Zn concentration and TM source on the immune function and associated biomarkers of immune status in weaned beef calves received into a feedlot. In this study, the more bioavailable, organic TM source supplemented to steers during receiving positively influenced growth rate and feed efficiency. Plasma TM concentration of steers in this study was adequate and was minimally influenced by TM source or concentration. These results also show TM supplementation, regardless of source, can alter markers of activation within immune cell populations.

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

Ninety-two Angus-crossbred steers (424 ±â€…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.

The Crossroads between Zinc and Steroidal Implant-Induced Growth of Beef Cattle.

Growth-promoting technologies such as steroidal implants have been utilized in the beef industry for over 60 years and remain an indispensable tool for improving economic returns through consistently improved average daily gain via increased skeletal muscle hypertrophy. Zinc has been implicated in skeletal muscle growth through protein synthesis, satellite cell function, and many other growth processes. Therefore, the objective of this review was to present the available literature linking Zn to steroidal implant-induced protein synthesis and other metabolic processes. Herein, steroidal implants and their mode of action, the biological importance of Zn, and several connections between steroidal implants and Zn related to growth processes are discussed. These include the influence of Zn on hormone receptor signaling, circulating insulin-like growth factor-1 concentrations, glucose metabolism, protein synthesis via mTOR, and satellite cell proliferation and differentiation. Supplemental Zn has also been implicated in improved growth rates of cattle utilizing growth-promoting technologies, and steroidal implants appear to alter liver and circulating Zn concentrations. Therefore, this review provides evidence of the role of Zn in steroidal implant-induced growth yet reveals gaps in the current knowledge base related to optimizing Zn supplementation strategies to best capture growth performance improvements offered through steroidal implants.

Effects of increasing doses of trenbolone acetate and estradiol on finishing phase growth performance, carcass trait responses, and serum metabolites in beef steers following implantation.

Yearling Simmental × Angus crossbred beef steers (n = 240; allotment BW = 365 ± 22.5 kg) from a South Dakota auction facility were transported 117 km to Brookings, SD and used in a randomized complete block design feedlot study to evaluate the effects of implants (both from Zoetis, Parsippany, NJ) containing increasing doses of trenbolone acetate (TBA) and estradiol benzoate (EB) administered 124 d prior to harvest have on finishing phase growth performance, carcass characteristics, and serum concentrations of urea-N (SUN) and insulin-like growth factor I (IGF-I). Thirty pens (10 pens/treatment) were assigned to 1 of 3 treatments: 1) negative control given no implant (NI); 2) a steroidal implant containing 100 mg TBA and 14 mg EB administered subcutaneously in the center one-third of the ear on day 1 (Synovex Choice, Zoetis, Parsippany, NJ; CH); 3) a steroidal implant containing 200 mg TBA and 28 mg EB administered subcutaneously in the center one-third of the ear on day 1 (Synovex Plus, Zoetis; PL). Cattle were fed for 124 d post-implantation. Steers were fed a common diet throughout the study. Treatment effects were evaluated by the use of orthogonal polynomials. Pen was the experimental unit for all analyses; an α of 0.05 determined significance. There was a quadratic effect (P = 0.01) on carcass-adjusted final BW. Increasing doses of TBA and EB resulted in a linear increase for both average daily gain (P = 0.01) and dry matter intake (P = 0.02). A quadratic effect on gain-to-feed ratio was observed (P = 0.01). No quadratic (P ≥ 0.40) or linear (P ≥ 0.14) effects were observed for dressing percentage, rib fat (RF), calculated yield grade, or marbling scores. A quadratic increase (P = 0.01) in hot carcass weight (HCW) and a linear increase (P = 0.01) in ribeye area (REA) were detected. No significant implant × day interaction (P ≥ 0.09) was noted for serum concentrations of urea-N or IGF-I. Implants decreased (P = 0.01) SUN compared with NI. Serum concentration of IGF-I was increased (P = 0.04) in implanted steers compared with NI steers. In yearling crossbred beef steers, the use of steroidal implants containing a combination of 100 mg TBA + 14 mg EB or 200 mg TBA + 28 mg EB increases growth performance, HCW, and REA at equal RF accumulation without detriment to marbling score compared with nonimplanted steers.

Increasing hay inclusion in silage-based receiving diets and its effects on performance and energy utilization in newly weaned beef steers.

The influence of grass hay (GH) inclusion in replacement of corn silage in receiving diets on growth performance and dietary net energy (NE) utilization was evaluated in newly weaned beef steers (n = 162 Charolais-Red Angus cross steers; initial body weight [BW] = 278 ± 13.4 kg). Treatments were (DM basis): 1) 0% GH, 2) 10% GH, or 3) 20% GH inclusion in replacement of corn silage in receiving diets fed to newly weaned beef steers for 56 d. The study was conducted from October to December of 2019. Data were analyzed as randomized complete block design with pen serving as the experimental unit for all analyses. Increasing dietary inclusion of hay had no influence (P ≥ 0.11) on final BW, ADG, gain:feed or observed/expected dietary NEM and NEG, observed/expected dry matter intake (DMI), or observed/expected ADG. GH inclusion increased (linear effect, P = 0.01) DMI. Observed DMI for all treatments was approximately 15% to 17% less than anticipated based upon steer growth performance and tabular NE values. Evaluation of observed/expected ADG was 31% to 37% greater than expected for the steers in the present study. Particles less than 4 mm increased (linear effect, P = 0.01) and greater than 4 mm decreased (linear effect, P = 0.01) as GH replaced corn silage in the receiving diet. As the proportion of particles greater than 4 mm increased, cumulative ADG was decreased. These data indicate that GH should be considered in corn silage-based receiving diets to improve DMI. In high-risk calves, improved DMI could result in a lesser incidence of morbidity, although no morbidity was observed in any steers from the present study.

Evaluation of batch fraction, corn silage inclusion level, and mixing duration on long particle distribution of finishing diets for beef cattle.

Background:  Differing fractions of a batch of feed, differing ingredient characteristics, and inadequate mix time can lead to non-uniformity within a mix of feed.  Methods: The experiment was designed as a 5 x 2 x 2 factorial arrangement with seven replications per simple treatment mean. Factors included: 1) batch fraction (BF; n = 5); 2) corn silage inclusion level (CSLVL; n = 2) 15% or 30% inclusion (dry matter basis); and 3) mixing duration (DR; n = 2) of 20 or 25 mixer revolutions. Data were analyzed as a completely randomized design using a binomial approach. The Penn State Particle Separator was used to separate fractions of the total mixed ration (TMR). Results: No interactions between BF, CSLVL, and DR were detected ( P ≥ 0.31) for any dependent variables. There was an increase ( P = 0.01) in retention on the 19 mm sieve from the first BF compared to the last BF. CSLVL altered ( P = 0.01) retention on the 19 mm sieve. Increasing DR from 20 to 25 revolutions had no appreciable influence ( P = 0.23) on particles greater than 19 mm.  CSLVL ( P = 0.01) and DR ( P = 0.01) altered particle retention on the 8 mm sieve. BF ( P = 0.01), CSLVL ( P = 0.01), and DR ( P = 0.02), influenced particle retention on the 4 mm sieve. CSLVL impacted ( P ≤ 0.01) particles remaining in the bottom pan and particles greater than 4 mm. BF ( P = 0.01) and CSLVL ( P = 0.01) altered particles greater than 8 mm. Conclusions: These data indicate that BF and CSLVL fed alters particle size distribution that in turn could alter dry matter intake, dietary net energy content, and influence daily gain. Mixing DR had no appreciable influence on particle size distribution of the TMR.