156 Evaluation of Long Acting Combination Implants Containing Trenbolone Acetate and Estradiol-17β on Live Performance, Carcass Traits, and Sera Metabolites in Finishing Steers

• Published in: Journal of animal science Vol. 96; no. suppl_2; pp. 82 - 83
• Main Authors: Smith, Z K F, Thompson, A J, Hutcheson, J P, Nichols, W T, Johnson, B J
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 10.04.2018
• Subjects: implant; beef; steer
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/sky073.153

Abstract 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 long acting 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 (uncoated) and 120 mg TBA + 24 mg E2 (coated); XS], Revalor-200 on d 0 [200 mg TBA + 20 mg E2 (uncoated); 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; XR and XS were intermediate (P > 0.10), not differing from others. 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) serum 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 anabolic constituents congruently to D200. The greatest dose of E2, contained in XS, provided improvements in gain and carcass weight without detriment to marbling scores compared to NI.