title: Anabolic payout of terminal implant alters adipogenic gene expression of the longissimus muscle in beef steers.
abstract: This experiment evaluated the dose and payout pattern of trenbolone acetate (TBA) and estradiol-17β (E) on LM mRNA expression of adenosine monophosphate-activated protein kinase-ɑ (-ɑ), β, G protein-coupled receptor 41(), G protein-coupled receptor 43 (), γ, and stearoyl CoA desaturase () in finishing feedlot steers as indicators of adipogenesis and marbling development. British × Continental steers (n = 168; 14 pens/treatment; initial BW = 362 kg) were used in a randomized complete block design. Treatments included: no implant (NI), Revalor-S (REV-S; 120 mg TBA + 24 mg E), or Revalor-XS (REV-X; delayed release implant: 80 mg TBA + 16 mg E [uncoated], 120 mg TBA + 24 mg E [coated], 200 mg TBA + 40 mg E [total]). Steers were fed 1 time daily for an average of 164 d. The LM biopsies were collected (1 steer/pen) on d -1, 27, 55, and 111 relative to timing of implant. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure quantity of -ɑ, β, , ,it, γ, and mRNA. No implant × day interactions were detected ( ≥ 0.19) in this experiment. Day impacted the mRNA expression of all adipogenic genes ( ≤ 0.02). The main effect of implant tended ( = 0.09) to influence expression of -ɑ, REV-X had an 8.8% increase over NI and an 18.7% increase over REV-S. Implant influenced ( = 0.03) mRNA expression of , expression of for the REV-X treatment was not different ( > 0.10) from NI, and both were greater ( ≤ 0.05) than REV-S (1.13, 1.00, and 0.67 ± 0.224 arbitrary units) for REV-X, NI, and REV-S, respectively. Implant also influenced ( = 0.02) expression of , expression of for REV-X was not different ( > 0.10) from NI, and both were greater ( ≤ 0.05) than REV-S (1.27, 1.07, and 0.72 ± 0.234 arbitrary units) for REV-X, NI, and REV-S, respectively. Implant influenced ( = 0.02) mRNA expression of γ in LM tissue, expression of γ for REV-X was not different ( > 0.10) from NI, and both were greater ( ≤ 0.05) than REV-S (1.09, 1.02, and 0.69 ± 0.195 arbitrary units) for REV-X, NI, and REV-S, respectively. The REV-X steers received the greatest anabolic dose of TBA + E without detriment to marbling scores. The increased mRNA expression of adipogenic genes for REV-X steers suggest that the delayed and gradual release of anabolic stimulants associated with REV-X might have mitigated decreases in marbling generally attributed to multiple combined TBA + E implants.
authors.forename: Z K
authors.initials: ZK
authors.lastname: Smith
authors.forename: K Y
authors.initials: KY
authors.lastname: Chung
authors.forename: S L
authors.initials: SL
authors.lastname: Parr
authors.forename: B J
authors.initials: BJ
authors.lastname: Johnson
mesh_terms: D050156:Adipogenesis / Q000187:drug effects* / Q000502:physiology; D045930:Anabolic Agents / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D004338:Drug Combinations; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D014204:Trenbolone Acetate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D045930:Anabolic Agents; D003692:Delayed-Action Preparations; D004338:Drug Combinations; D004343:Drug Implants; D012333:RNA, Messenger; C021828:Revalor; D004958:Estradiol; D014204:Trenbolone Acetate