Comparative effects of ractopamine hydrochloride and zilpaterol hydrochloride on growth performance, carcass traits, and longissimus tenderness of finishing steers1

Abstract

Ractopamine hydrochloride (RAC) and zilpaterol hydrochloride (ZH) are beta-adrenergic agonists that improve growth performance and affect carcass characteristics. The objective of this study was to evaluate the comparative effects of RAC and ZH when fed to beef steers during the last 33 d of the finishing period. Three hundred crossbred beef steers (516 +/- 8 kg) were grouped by BW, BCS, and breed type and randomly assigned to 1 of 3 treatments (10 steers per pen; 10 pens per treatment). Treatments were control (no beta-agonists added), RAC (200 mg of ractopaminexhdx(-1)d(-1), for 33 d), or ZH (75 mg of zilpaterolxanimalx(-1)d(-1), for 30 d, removed 3 d for required withdrawal period). Steers were slaughtered, carcass characteristics were evaluated, and cut-out yields were determined. Both RAC and ZH increased final BW, ADG, feed efficiency (G:F), and HCW compared with controls (P < 0.05). Compared with RAC, ZH decreased ADG, ADFI, and final BW, but increased HCW and dressing percentage (P < 0.05). Carcass yield was not affected by RAC in this experiment, whereas ZH decreased adjusted fat thickness and KPH, increased ribeye area, improved yield grade, and increased cut-out yields, when compared with controls (P < 0.05). Marbling, lean maturity, and skeletal maturity were not different between treatments (P > 0.05). Steaks from RAC steers had greater (P < 0.05) Warner-Bratzler shear force (WBSF) values than steaks from control steers at 3 and 7 d of aging, but did not differ from controls after 14 d of aging. Steaks from ZH steers had greater WBSF values (P < 0.05) than steaks from controls and RAC steaks throughout the 21-d postmortem aging period. Although both beta-adrenergic agonists were effective at improving feedlot performance, RAC showed no negative effect on WBSF after 14 d, whereas WBSF values for ZH steaks were significantly greater than controls after 21 d.

Effects of ractopamine hydrochloride and dietary protein content on performance, carcass traits and meat quality of Nellore bulls

“…In general, feeding ractopamine increases average daily gain, improves feed efficiency and increases both live and hot carcass weight (HCW) (Schroeder, 2004;Dunshea et al, 2005;Avendaño et al, 2006). This increase in muscle mass is attributed to an increase in muscle protein synthesis, a reduction in protein degradation or some combination of both (Scramlin et al, 2010). In addition, other β-AA increase the transcriptional activity of calpastatin (Rathmann et al, 2009), which could be the reason for the reduction in tenderness that has been reported in some studies (Leheska et al, 2008;Kellermeier et al, 2009).…”

“…In December 2011 the use of ractopamine in feedlot cattle was approved in Brazil. The efficacy of β-AA has been demonstrated in several studies with mostly young, castrated, Bos taurus breeds, with a high degree of fat thickness, and marbling (Gruber et al, 2007;Quinn et al, 2008;Scramlin et al, 2010). However, the efficacy of β-AA has yet to be demonstrated in Bos indicus intact bulls, with reduced fat thickness (slaughter at 20% carcass fat), a common situation in Brazilian herds.…”

Agonistas beta-adrenérgicos como aditivo para bovinos de corte

“…dos bovinos possuir maior proporção de receptores do tipo β2 (Johnson et al, 2014) (scraMlin et al, 2010).…”

“…A adição de ractopamina na dieta não influenciou a espessura de gordura de bovinos confinados comparados a animais que não receberam esse aditivo (aVendaño-reyes et al, 2006;quinn et al, 2008;scraMlin et al, 2010) …”

Effects of active immunization against the recombinant second extracellular loop of sheep β₂-adrenoceptor on growth and blood biochemical parameters of female rats

“…β-adrenoceptors (β-ARs) are involved in adipose tissue lipolysis and protein deposition in human and animal modulated by β-agonists (Langin, 2006). Carcass composition and feed efficiency of domestic animals can be improved by using β-agonists, such as clenbuterol, ractopamine and zilpaterol (Scramlin et al, 2010). However, detrimental effects of these compounds are also obviously.…”