The impact of copper status on lubabegron fumarate-induced growth and adipose immune cell infiltration in beef feedlot steers

Lay Summary Lubabegron fumarate (LUB; tradename Experior, Elanco Animal Health, Greenfield, IN, US) is a novel beta-adrenergic agonist that possesses a unique mechanism of action compared to other beta-agonists used in the beef industry. Previous research has noted that high liver copper (Cu) concentrations resulted in an impaired growth response in steers fed ractopamine hydrochloride. In the present study, a similar interaction occurred between liver Cu concentration and LUB-induced growth, in which steers supplemented with 10 mg Cu/kg diet DM (liver Cu 301 mg Cu/kg liver DM) exhibited a lesser response to LUB than steers fed no supplemental Cu with marginal liver Cu concentrations (50 mg Cu/kg liver DM). Additionally, this study suggests that LUB improves growth performance and lean tissue accretion, at least in part, through improved insulin sensitivity. Further, this is the first study to examine mononuclear phagocyte infiltration into adipose tissue over time, demonstrating the ability to characterize changes in adipose inflammation over the finishing period. These results highlight the need for refined Cu requirements in beta-agonist-fed animals as well as further research into LUB mechanism of action.