Effects of feeding lubabegron fumarate or ractopamine hydrochloride to beef × dairy crossbred steers raised under small-pen commercial feedlot conditions in western Canada

This study evaluated the effects of feeding lubabegron fumarate compared with ractopamine hydrochloride in beef × dairy crossbred steers fed a corn-based diet in western Canada. Beef × dairy (Limousin × Jersey) crossbred steers (n = 760, initial BW = 530.0 ± 34.7 kg) were randomly allocated 80 d before slaughter to 1 of 2 experimental groups. A total of 20 replicates were allocated to the study, with each replicate comprising 1 pen from each experimental group (for a total of 40 pens) and 19 steers per pen. Pen was the experimental unit. Experimental groups consisted of either lubabegron fumarate (Experior 10, Elanco Canada Limited, Mississauga, Canada) fed at a target level of 3.5 mg/kg diet DM for 56 d before slaughter (EXP) or ractopamine hydrochloride (Optaflexx 100, Elanco Canada Limited) fed at a target level of 250 mg/steer daily the last 28 d before slaughter (RAC). Steers in the EXP group had lower DMI, greater carcass weight, and greater DP compared with steers in the RAC group. Steers in the EXP group had greater ADG and G:F on both a carcass weight and live weight basis compared with steers in the RAC group. Steers in the EXP group also had a greater proportion of YG Canada 1 carcasses, a lower proportion of QG Canada Prime carcasses, increased LM area, and a lower overall marbling score compared with steers in the RAC group. Feeding lubabegron fumarate increased feedlot performance, the proportion of YG Canada 1 carcasses, and LM area, but decreased the proportion of QG Canada Prime carcasses and overall marbling score compared with feeding ractopamine hydrochloride. Magnitude of improvement in G:F was greater on a carcass weight basis than on a live weight basis.