Abstract A feedlot finishing experiment was conducted to evaluate the impact of feeding Lubabegron (LUB; Experior; Elanco Animal Health; Greenfield, IN) or Ractopamine Hydrochloride (RAC; Optaflexx; Elanco Animal Health; Greenfield, IN) on feedlot performance, carcass characteristics, and meat quality attributes. Crossbred steers (n = 621; initial BW = 308 kg; SD = 16.1 kg) were utilized in a generalized randomized block design. Treatments included (1) feeding RAC at 300 mg/steer daily for 34-d (plus 2-d withdrawal prior to harvest) or (2) feeding LUB at 36 mg/steer daily for 42-d (plus 4-d withdrawal). Steers were blocked by arrival date at feedlot entry and a health monitoring treatment, and pens were assigned randomly to the two treatments within block. Cattle were weighed on the day that block one received LUB (on d 133), with a 4% shrink applied, and no initial weight differences were observed between treatments (P = 0.89). Performance data represent the entire feeding period. Steers fed LUB exhibited greater average daily gain, a 5% improvement in feed efficiency, and 10 kg heavier carcass weight (P 0.01). Steers fed LUB had larger ribeye area (P 0.01), similar 12th rib fat thickness (P = 0.73), and lower marbling score (P 0.01) compared to steers fed RAC. Quality grade distribution differed (P = 0.02), with RAC-fed steers producing a greater proportion of Prime and upper two-thirds Choice carcasses and fewer low Choice or select carcasses compared with LUB. A subset of 160 USDA Choice strip loins (four per pen) were collected to evaluate meat quality. Steers fed RAC were more tender, particularly at 7-d postmortem (P 0.01), with a significant treatment x aging interaction (P 0.01). Cooking loss did not differ between treatments or aging period (7 vs. 21 d). Lightness (L*) was unaffected by treatment, however, RAC-fed steers produced steaks with greater redness (a*; P 0.01) and yellowness (b*; P = 0.03). Overall, feeding LUB to beef steers increased carcass weight but reduced marbling and slightly reduced tenderness compared to RAC.
Smidt et al. (2026) studied this question.