Feedlot performance and biological responses to coated and non-coated steroidal implants containing trenbolone acetate and estradiol benzoate in finishing beef steers1,2,3

Abstract

Predominately Angus steers (n = 24; initial BW = 435 ± 28.3 kg) were used to evaluate non-coated (NC) and coated implants (CI) containing equal amounts of trenbolone acetate (TBA; 200 mg) and estradiol benzoate (EB; 28 mg) in finishing steers on sera metabolite responses, gene expression, and immunohistochemical analyses of the Longissimus muscle (LM). Performance data were analyzed as a randomized complete block design, and all other data were analyzed as repeated measures for a completely randomized design. Treatments were no implant (NI), NC (Synovex-PLUS; Zoetis, Parsippany, NJ), and CI (Synovex-One Feedlot) implant. There were 2 pen replicates per treatment (n = 4 steers/pen). LM biopsies, blood, and BW were collected before feeding on days 0, 14, 28, 56, 84, 112, and 133, with final BW being captured on day 140. Genes of interest were determined by RT-qPCR using two housekeeping genes. Sera was analyzed for estradiol-17β (E2),17β-trenbolone (TbOH), insulin-like growth factor 1 (IGF-I), NEFA, and urea-N (SUN). An α of 0.10 determined significance for performance and sera data; α of 0.05 was used for gene and histology data. No performance differences (P ≥ 0.10) were detected. An implant × day interaction (P ≤ 0.10) for E2, IGF-I, and SUN was detected; implants elevated (P ≤ 0.10) E2, 17β-TbOH, and IGF-I; and decreased SUN across day of the study, meaning sera metabolites are not altered with time on feed. An implant × day interaction was detected for myogenic factor 5 (MYF-5) positive cells and proportions of MHCIIX. In LM, CI had greater (P < 0.10) IGF-I in LM over NI. CI increased (P < 0.05) G protein-coupled estrogen receptor 1 (GPER1) expression, as well as, GPER1 semi-quantitative scores over NI and NC. An implant × day interaction (P ≤ 0.05) for estrogen and androgen receptor-positive nuclei was detected; implants had increased (P ≤ 0.05) estrogen and androgen receptor-positive nuclei compared to NI. CIs increase genes associated with muscle tissue growth.

Keywords: beef; estradiol; insulin-like growth factor I; satellite cell; trenbolone.

Figure 1.

Sera metabolites responses to implant treatment: Negative control given no implant (NI); Synovex-PLUS (non-coated implant [NC]: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM). A: estradiol-17β (pg/mL), B: trenbolone-17β (pg/mL), C: IGF-I (ng/mL), D: NEFA (mEq/L), E: urea-N (mg/dL).

Figure 2.

Implant responses for mRNA abundance of G protein-coupled estrogen receptor 1 (GPER1). Treatments included: Negative control given no implant (NI); Synovex-PLUS (non-coated implant [NC]: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM).

Figure 3.

Implant responses for mRNA abundance of insulin-like growth factor I (IGF-1). Treatments included: Negative control given no implant (NI); Synovex-PLUS (non-coated implant [NC]: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM).

Figure 4.

Estrogen receptor (ER) positive nuclei (cells/mm²) (A), (B) androgen receptor (AR) positive nuclei (cells/mm²), (C) G protein-coupled estrogen receptor 1 (GPER-I) expression response to implant treatment: Negative control given no implant (NI); Synovex-PLUS (non-coated implant [NC]: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM). (D) Images of immunohistological staining of estrogen receptor-positive nuclei, androgen receptor-positive nuclei (both cells/mm²), and G protein-coupled estrogen receptor1 (GPER1) semi-quantitative score (Klein et al., 2001) in skeletal muscle fibers from bovine longissimus dorsi tissue biopsy. Biopsies were performed on days 0, 14, 28, 56, 84, 112, and 133. Panel (a) Nuclei, (b) GPER1, (c) estrogen receptor, (d) androgen receptor, and (e) all. In panel E, blue represents nuclei, green represents GPER1, yellow represents androgen receptor-positive, red represents estrogen receptor-positive.

Figure 5.

Implant responses to the change from day 0 for mRNA abundance of G protein-coupled estrogen receptor1 (GPER1). Treatments included: Negative control given no implant (NI); Synovex-PLUS (non-coated [NC] implant: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM).

Figure 6.

Images of immunohistological staining of satellite cell populations in skeletal muscle fibers from bovine longissimus dorsi tissue biopsy (A). Biopsies were performed on days 0, 14, 28, 56, 84, 112, and 133. Panel (a) Nuclei, (b) MYF5 positive cells, (c) paired box protein 7 (Pax7) positive satellite cells, and (d) Dual positive satellite cells expressing both MYF5 and Pax7. Blue represents nuclei, green represents MYF5 positive satellite cells, yellow represents Pax7 positive satellite cells. (B) Myonuclei density (cells/mm²) responses to implant treatment: Negative control given no implant (NI); Synovex-PLUS (non-coated implant [NC]: 200 mg trenbolone acetate [TBA] and 28 mg estradiol benzoate [EB]) administered subcutaneously in the center one-third of the ear on day 0; Synovex-ONE Feedlot (coated implant [CI]: 200 mg TBA and 28 mg EB; coated and a delayed-release implant) administered subcutaneously in the center one-third of the ear on day 0. Least squares means; pooled implant × day standard error of the mean (SEM).

Figure 7.

Changes in proportion of muscle fiber types in Longissimus muscle overtime on implantation (NI: no implant, NC: non-coated implant containing 200 mg of TBA and 20 mg of EB, CI: coated implant containing 200 mg of TBA and 20mg of EB). (A) percentage of myosin heavy chain (MHC) I, (B) IIA, (C) IIX. Least squares means; pooled implant × day standard error of the mean (SEM).

Figure 8.

Changes in cross-section area of (A) MHCI, (B) IIA, and (C) IIX positive fibers in Longissimus muscle of steers, as affected by coated or non-coated implants overtime (NI: no implant, NC: non-coated implant containing 200 mg of TBA and 20 mg of EB, CI: coated implant: coated implant containing 200 mg of TBA and 20 mg of EB). Least squares means; pooled implant × day standard error of the mean (SEM). (D) Images of immunohistological staining myosin heavy chain in the longissimus dorsi tissue biopsy. Biopsies were performed on days 0, 14, 28, 56, 84, 112, and 133. Green is dystrophin, orange is MHCI, red is MHCIIA, and black is MHCIIX.