Effects of ractopamine hydrochloride supplementation on feeding behavior, growth performance, and carcass characteristics of finishing steers1,2

Abstract

Ractopamine hydrochloride (RAC) is a β-adrenergic agonist that functions as a repartitioning agent to improve muscling in feedlot cattle. Many studies have investigated the effects of RAC on growth performance and carcass characteristics; however, there is minimal information about the influence of RAC on feeding behavior. Sixty-nine steers (body weight [BW] = 364 ± 3.9 kg) predominately of Angus and Simmental breeding were subjected to a 126-d (n = 46) or 154-d (n = 23) feeding period and randomly assigned to one of two treatment groups: supplementation to provide 0 (CON; n = 34) or 267 ± 4.9 mg/d of RAC (n = 35). Ractopamine was provided as Optaflexx 45 at 0.024% of the diet (dry matter [DM] basis; Elanco Animal Health, Greenfield, IN). Dietary treatments were fed the final 42 d in the feed yard (treatment period). Feeding behavior and growth performance were measured using radio frequency identification tags and the Insentec feeding system. Following the final day of treatment, steers were slaughtered and carcass measurements were recorded. Data were analyzed using MIXED models in SAS. There were no differences in BW, average daily gain (ADG), DM intake (DMI), gain:feed ratio (G:F), or feeding behavior during the pretreatment period (P > 0.44). Ractopamine supplementation increased G:F during the treatment period (P = 0.02) and during the total period (P = 0.03) and tended to increase ADG during the treatment and total period (P ≤ 0.08). DMI was not affected during the treatment or total period (P > 0.67). Eating time per visit, per meal, and per day were decreased (P < 0.02) in steers supplemented with RAC during the treatment period. DMI per minute was increased (P = 0.02) in steers supplemented with RAC. Hot carcass weight, dressing percentage, and 12th rib fat were not influenced by RAC supplementation. Ractopamine supplementation decreased marbling (P = 0.008) and kidney, pelvic, and heart percentage (P = 0.04) and increased longissimus muscle area (P = 0.01). These data demonstrate that RAC supplementation for 42 d improves feed efficiency, increases the rate of DMI without altering DMI, and increases muscling in finishing cattle.

Cattle and carcass performance, and life cycle assessment of production systems utilizing additive combinations of growth promotant technologies

“…Supplementation with RH did not improve the HCW or LM area of the BA treatment compared to IMP but resulted in advanced carcass maturity. Others have reported no difference in HCW ( Quinn et al, 2008 ; Strydom et al, 2009 ; Hales et al, 2016 ; Hunter-Beasley, et al, 2018 ; Trotta et al, 2019 ) or LM area ( Walker et al, 2006 ; Quinn et al, 2008 ; Strydom et al, 2009 ; Hales et al, 2016 ; Hunter-Beasley, et al, 2018 ) of RH supplemented cattle compared with non-supplemented controls. However, it is unclear why the LM area of BA was 4.6 cm 2 smaller than IMP in the present study.…”

Immunological effects of ractopamine in rabbits receiving the viral inactivated rabbit hemorrhagic disease vaccine

“…Ractopamine is also used to favor the FCR in the livestock industry ( Hales et al 2016 ). Besides, Ronald et al (2019 ) reported that ractopamine could induce a significant rise in weight gain and improve FCR. Likely, Abd-elfattah et al (2019 ) stated that vaccination with the RHD virus vaccine did not significantly affect body weight and FCR.…”

“…Beta-agonists effectively stimulate cattle growth ( Kootstra et al , 2005 ). It is used to enhance physical performance ( Ronald et al , 2019 ). According to Mirhendi et al (2014 ), beta-adrenergic agonists enhance the growth performance of chicken.…”

Effects of protein concentration and beta-adrenergic agonists on ruminal bacterial communities in finishing beef heifers

“…Indeed, when supplemented with RAC at 300 mg/d for 28 d, steers had a greater number of daily feeding events and those events were in shorter duration [ 44 ]. In contrast, when feeding RAC over a longer 42 d period, visit eating time, per meal, and per day were reduced in steers [ 45 ]. Further, when RAC was supplemented at 200 mg/d for 30 d, steers had an extended time required to consume daily feed [ 33 ].…”