Additive effects of a steroidal implant and zilpaterol hydrochloride on feedlot performance, carcass characteristics, and skeletal muscle messenger ribonucleic acid abundance in finishing steers1

Abstract

This experiment investigated the effects of zilpaterol hydrochloride (ZH) and the steroidal implant Revalor-S (RS; 120 mg of trenbolone acetate and 24 mg of estradiol-17beta) on finishing steer performance and the mRNA concentration of beta-adrenergic receptors (beta-AR) types I and II, and types I, IIA, and IIX myosin heavy chain (MHC) isoforms. A total of 2,279 feedlot steers weighing 426 +/- 6.4 kg were administered no implant or RS on d 0, and fed 0 or 8.3 mg of ZH/kg of diet DM during the last 30 d with a 3-d withdrawal. Treatments were randomly assigned to 24 pens (n = 6 pens/treatment). At slaughter, semimembranosus muscle tissue was excised for RNA isolation from 4 carcasses per pen. No interactions were detected for any of the variables measured in the experiment. Administration of ZH during the last 30 d of the feeding period increased (P < 0.01) ADG, G:F, HCW, and LM area; decreased (P < 0.01) 12th-rib fat depth and marbling; and improved (P < 0.01) yield grade. Treatment had no effect on beta1-AR mRNA levels, but there was an increase (P = 0.01) in beta(2)-AR mRNA levels due to ZH inclusion. Myosin heavy chain-I (MHC-I) mRNA levels were unaffected by treatment. For MHC-IIA mRNA concentrations, administration of RS tended (P = 0.08) to increase mRNA levels, whereas ZH feeding the last 30 d tended (P = 0.08) to decrease mRNA levels for this isoform of myosin. Feeding ZH the last 30 d before slaughter increased (P < 0.01) mRNA concentrations of MHC-IIX in semimembranosus muscle of steers. These data indicate the combined use of ZH and RS additively contributes to BW and carcass gain in finishing feedlot steers and decreases marbling scores and USDA quality grades. The LM area increased and fat thickness decreased. In addition, ZH feeding changes the mRNA levels of MHC isoforms to a faster, more glycolytic fiber type in bovine skeletal muscle. These changes in mRNA concentrations of MHC isoforms, due to ZH feeding, could be affecting skeletal muscle hypertrophy.

Non-inferiority trial of two commercial zilpaterol HCl brands in <em>Bos indicus</em> cattle under humid tropical conditions

“…54 Although consumers detected differences in the Longissimus dorsi muscle juiciness for both ZH treatments, the overall pleasing rating was unaffected (P = 0.046; Wald c 2 test = 6.2; d.f = 1). This agrees with the results of Garmyn 36 , who indicated that ZH does not modify Longissimus dorsi muscle taste from Holstein bulls compared with control samples. Despite sustained juiciness and general softness scores being affected, it is likely that these latter changes were related to the lesser amount of intramuscular fat in the ZH-treated animal meat.…”

“…The magnitude of improvement in final body weight (22 %), lies near the maximum value reported in the literature (25 %), using the reference brand ZH. 4,[31][32][33][34][35][36][37][38][39] For example, weight gain coincides greatly with other studies conducted on Bos taurus bulls. 34,40 Elam et al treated Bos taurus bulls with 8.33 mg ZH/kg feed as dry matter for 30 days and obtained final weight increments of 9.3 kg compared with untreated bulls.…”

Modification of muscle inherent properties through age at slaughter, growth promotants and breed crosses

“…Why this occurred is unclear, as fibre populations were similar in the ST muscles of control steers of each breed. b-AA and IMP can be additive on carcass characteristics (Strydom et al 2009;Baxa et al 2010), but RAC and the hormonal effects of IMP have not been shown to be synergistic (Bass et al 2009). Gonzalez et al (2010) incorporated different breeds into a study on the effect of RAC on muscle fibre morphology, but were unable to assess breed effect as it was confounded with kill group.…”

Effect of growth-promoting technologies on Longissimus lumborum muscle fiber morphometrics, collagen solubility, and cooked meat tenderness12

“…Kellermeier et al (2009) conducted a similar study in steers and reported that average muscle fiber diameter increased by 3% and 6% when anabolic implants and ZH were utilized, respectively. While Rathmann et al (2009) and Baxa et al (2010) did not directly measure fiber CSA or diameter, they did indicate increases in the mRNA expression of type IIX muscle fibers demonstrated ZH increased protein synthesis of this isoform. Other B-AA have also increased muscle fiber CSA.…”