Effect of ractopamine hydrochloride (Optaflexx) dose on live animal performance, carcass characteristics and tenderness in early weaned beef steers

Study objectives were to evaluate ractopamine hydrochloride's (RAC) effect on performance, carcass characteristics, and tenderness of early weaned beef steers. Steers were assigned to a control diet (0mgRAC·steer ^-1·d ^-1), 200mgRAC mg·steer ^-1·d ^-1, or 300mgRAC·steer ^-1·d ^-1. Steers fed 200 and 300mgRAC·steer ^-1·d ^-1 gained 14.84kg and 14.57kg more live weight and produced 13.22 and 14.90kg more hot carcass weight, respectively, than controls. Feed conversions for steers fed 200 or 300mgRAC·steer ^-1·d ^-1 of RAC increased 45.2% and 47.3% and average daily gain increased 55.5% and 54.5% compared to controls, respectively. Feeding either dose of RAC increased (P<0.05) loin muscle area and increased (P<0.05) Warner-Bratzler shear force (WBSF) values compared to controls, however the magnitude of WBSF difference diminished (P>0.05) over 14days of postmortem aging. Results of this study confirm that RAC increases weight gain and feed efficiency, minimally impacts carcass quality and has manageable impacts on tenderness when fed at either 200 or 300mgsteer ^-1·d ^-1.