Administration of estradiol, trenbolone acetate, and trenbolone acetate/estradiol implants alters adipogenic and myogenic gene expression in bovine skeletal muscle

Abstract

Twenty crossbred yearling steers (421 kg) were used to evaluate the effects of implanting with trenbolone acetate (TBA; 120 mg), estradiol-17β (E(2); 25.7 mg), and a combination (120 mg of TBA and 24 mg of E(2)) on adipogenic and myogenic mRNA concentrations. Animals were blocked by BW and within each block were assigned to 1 of 4 treatments. Animals were housed and fed in individual pens with 5 animals per treatment. All animals were weighed weekly, and muscle biopsy samples were taken from the LM of each steer on d 0 (before implantation), 7, 14, and 28. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure the quantity of C/EBPβ, PPARγ, stearoyl CoA desaturase (SCD), myogenin, and 3 isoforms of bovine myosin heavy chain (MHC) mRNA. Total BW gain from the 28-d period was adjusted to d 0 by use of covariant analysis, and steers in the implant groups tended (P = 0.09) to have increased BW gain compared with nonimplanted control steers. Analysis of the gene expression of MHC showed that neither implant nor day (P > 0.20) had a significant effect on the expression of type I or IIX MHC mRNA There was also no treatment effect (P > 0.20) on MHC-IIA and myogenin, but increasing days on feed increased (P = 0.05) the expression of MHC-IIA mRNA. Relative mRNA abundance of C/EBPβ, PPARγ, and SCD increased (P < 0.05) during days of feed but PPARγ decreased (P < 0.05) with the treatment of combined TBA/E(2) implant. Results of this study indicate that implanting with TBA, E(2), or both increased BW gain and decreased adipogenic gene expression of finishing steers without significantly affecting the concentration of type I, IIA, or IIX MHC mRNA. Increasing days on feed increased both MHC-IIA and adipogenic gene expression in bovine skeletal muscle biopsy samples. We conclude that administration of steroidal implants had no effect on the proportion of the 3 MHC mRNA isoforms but decreased C/EBPβ, PPARγ, and SCD mRNA in bovine skeletal muscle.

Adipogenic gene expression and fatty acid composition in subcutaneous adipose tissue depots of Angus steers between 9 and 16 months of age1

“…Other studies of bovine adipose tissue explants (Hosseini et al, 2010) and bovine liver (Janovick-Guretzky et al, 2007) also demonstrated that RPS9 mRNA expression was stable and suitable as a normalization gene under their conditions. Additionally, RPS9 was used as a normalization gene for the expression of genes in bovine muscle (Baxa et al, 2010;Chung et al, 2011).…”

Steroid implants and markers of bone turnover in steers

“…Serum was then obtained by centrifugation (1 500 × g, for 20 min at 4 °C), divided into aliquots and stored at −20 °C until use. Steer management, including diet and implantation protocol, were identical to a companion study reported previously (Chung et al, 2012). In brief, the diet was a steam flaked maize and ground lucerne hay based diet that provided (dry matter basis) 135.6 g crude protein, 141.5 g neutral detergent fibre, 19.3 MJ NE m /kg and 13.1 MJ NE g /kg.…”

The effect of different implant programs on beef × dairy steer feedlot growth performance and carcass characteristics

“…Results agree with similar studies that reported increased percentage USDA Prime or Choice and decreased percentage of USDA Select in steers administered lower or delayed potencies of TBA ( Parr et al, 2011 ; Kayser et al, 2019 ; Quinn et al, 2020 ). Other researchers have reported detrimental effects of TBA on marbling development ( Chung et al, 2012 ; Smith et al, 2017 ).…”