Anabolic payout of terminal implant alters adipogenic gene expression of the longissimus muscle in beef steers

Effects of Corn Silage Inclusion Level and Type of Anabolic Implant on Animal Growth Performance, Apparent Total Tract Digestibility, Beef Production per Hectare, and Carcass Characteristics of Finishing Steers

Simple Summary

Corn silage has long been a staple feed ingredient in cattle diets throughout the Midwest region of the United States. The most recent Feedlot Consulting Nutritionist Survey indicated that corn silage was the primary and secondary roughage source used in finishing diets by 37.5% of respondents. Using the entirety of the corn plant for feed allows for producers to quickly harvest feed tonnage. A common belief is that one should only include enough corn silage in a finishing ration to maintain rumen health. However, previous research conducted by our research group suggested that feeding increased levels of corn silage could increase the quantity of beef produced per hectare of cropland. Another aspect to consider when finishing cattle is implant type. Today a wide variety of implants are available, including polymer barrier coated and non-coated implants. Coated implants can provide an extended release of trenbolone acetate and estradiol for up to 200 days post-implantation. The objectives of the current study were to determine the influence of corn silage inclusion level and terminal implant type on animal growth performance, apparent total tract digestibility, carcass traits, and beef production per hectare of cropland in finishing steers harvested at common rib fat thickness.

Abstract

Maine-Anjou × Angus cross-bred steers (n = 156 steers; initial body weight (BW) 366 ± 37.2 kg) were used in a 132 d finishing study conducted at the Ruminant Nutrition Center (RNC) in Brookings, SD. Steers were blocked by weight (n = 5 BW blocks) and randomly assigned to an implant and dietary treatment of a randomized complete block design with each pen containing seven to eight steers (n = 20 pens). Dietary treatments consisted of (1) 15% (CS15) or (2) 30% corn silage (CS30) where corn silage displaced corn grain in the diet. Steers received one of two implants (both from Zoetis, Parsippany, NJ) containing equal doses of trenbolone acetate (TBA) and estradiol benzoate (EB): (1) Synovex PLUS (non-coated implant; 200 mg TBA and 28 mg EB; PLUS) or (2) Synovex ONE Feedlot (coated implant; 200 mg TBA and 28 mg EB; ONE-F). Bunks were managed using a slick bunk approach, and all diets contained dry matter (DM) basis 33 mg/kg monensin sodium. All steers were offered ad libitum access to feed, and feeding occurred twice daily in equal portions. There was no interaction between the implant and dietary treatment for any variables measured (p ≥ 0.08). Carcass-adjusted basis final BW, average daily gain (ADG), and grain to feed (G:F) were increased (p ≤ 0.02) by 2.2%, 6.5%, and 7.2%, respectively, for CS15. Observed net energy (NE) and the ratio of observed-to-expected NE for maintenance and gain was not influenced (p ≥ 0.15) by silage inclusion treatment. Beef production per hectare was not impacted (p ≥ 0.13) by corn silage inclusion level. Fecal output was increased, and digestibility coefficients for dry matter, organic matter, and crude protein were decreased in CS30 (p ≤ 0.03). Dressing percent and hot carcass weight (HCW) were greater (p ≤ 0.02) in CS15. Implant type did not influence any traits measured (p ≥ 0.14) except for marbling. Marbling was decreased for PLUS (433 vs. 466 ± 17.5; p = 0.02) compared to ONE-F steers. Similar beef produced per hectare of crop land-based upon silage feeding level means producers can feed greater inclusions of corn silage to finishing cattle without impacting carcass quality or beef production; implanting with a coated implant had no detrimental effects to growth performance but increases marbling scores.

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.

Evaluation of coated steroidal implants containing trenbolone acetate and estradiol-17β on live performance, carcass traits, and sera metabolites in finishing steers

Crossbred beef steers (n = 240; 12 pens/treatment; initial BW = 305 ± 17.7 kg) were used in a randomized block design feedlot study to evaluate the influence of coated trenbolone acetate (TBA) and estradiol-17β (E2) implants (Merck Animal Health, Madison, NJ) on gain performance, carcass traits, and sera metabolites. The five treatments were no implant (NI), Revalor-XR on d 0 [200 mg TBA + 20 mg E2 (coated); XR], Revalor-XS on d 0 [200 mg TBA + 40 mg E2 (total): 80 mg TBA + 16 mg E2 (noncoated) and 120 mg TBA + 24 mg E2 (coated); XS], Revalor-200 on d 0 [200 mg TBA + 20 mg E2 (noncoated); E200], or Revalor-200 on d 70 (D200). Interim BW and blood were collected on d 0, 14, 35, 70, 105, 140, and 175 prior to feeding and on d 213 prior to shipping. Following a 24 h clot at 4 °C, sera was harvested to quantify circulating E2, IGF-I, NEFA, serum urea-N (SUN), and 17β-trenbolone (17β-TbOH). Implanted steers had greater (P ≤ 0.05) ADG, G:F, and final BW than NI controls. Implants increased (P < 0.05) HCW by 8%, 366 vs. 391, 414, 380, and 396 ± 6.4 kg, for NI vs. XR, XS, E200, and D200, respectively. The greatest (P ≤ 0.05) dressing percentage, yield grade, and calculated empty body fat occurred in XS, which had greater (P < 0.05) rib fat than NI, XR, and D200. Marbling scores in NI were greater (P < 0.05) than E200 and D200; steers in XR and XS were intermediate (P > 0.10), not differing from NI, E200, or D200. An implant × day interaction (P ≤ 0.01) was noted for circulating E2, IGF-I, SUN, and 17β-TbOH. Implanted steers had elevated (P ≤ 0.05) sera E2, IGF-I, and 17β-TbOH, and decreased (P < 0.05) SUN following implantation compared to NI controls. Serum NEFA differed (P < 0.01) over time, but did not differ (P > 0.10) due to implant treatment. These data indicated that the polymer coating applied to the XR implant delayed release of steroidal hormones congruently to D200, with no negative impact on marbling. The greatest dose of E2, contained in XS, provided improvements in gain and carcass weight without detriment to marbling scores compared to NI.