Cattle, carcass, economic, and estimated emission impacts of feeding finishing steers lubabegron or ractopamine hydrochloride

Abstract

Lubabegron (Experior; Elanco, Greenfield, IN, USA) is the first U.S. Food and Drug Administration approved feed additive for reducing gas emissions from feedlot animals or their waste; it does not have live or carcass performance claims. Our primary objective was to determine the effect of lubabegron on feedlot performance and carcass traits in finishing beef steers compared to ractopamine hydrochloride (Optaflexx; Elanco, Greenfield, IN, USA). A commercial feedlot trial using crossbred beef steers (n = 2,117; 373 ± 15 kg initial body weight [BW]) was completed with a randomized complete block design. Treatments consisted of two feed additives: 1) OPT targeted to deliver 300 mg/animal/d of ractopamine hydrochloride for 28 ± 7 d out from harvest and 2) EXP targeted to deliver 36 mg/animal/d of lubabegron 56 ± 7 d out from harvest and a 4-d pre-slaughter withdrawal period. Twenty 70-142 hd pens with 10 pens per treatment were used. Cattle were weighed at arrival processing and at harvest and fed for an average of 167 days. Data were used to calculate production metrics, partial budgets, and estimated greenhouse gas emissions using published methods, and were analyzed using linear mixed models with pen as the experimental unit and block as a random intercept. A statistical significance threshold of α = 0.05 was determined a priori. There was no evidence for statistically significant differences between treatments for initial BW (P = 0.70), health related outcomes (P values ≥ 0.43), or mobility scores (P = 0.09). Cattle fed EXP had increased final BW, ADG, G:F, and decreased DMI (P values ≤ 0.01) compared to OPT. Carcasses were 11 ± 1.76 kg (HCW) heavier in EXP group (P < 0.01), and differed between treatments for both YG and QG distributions (P values ≤ 0.01). Cattle fed EXP had a shift toward more YG 1 and 2, select and sub-select carcasses compared to OPT, which had as shift toward more YG 3, 4, 5, prime and choice carcasses. With increased beef production and efficiency compared to OPT, the estimated CO2 equivalent emissions from production were reduced 6.2% per unit of carcass weight for EXP (P ≤ 0.01). Estimated net returns/animal shipped were $56.61 ± 9.37 more for EXP than OPT (P ≤ 0.01). In conclusion, when cattle were fed for the same total number of days, feeding EXP compared to OPT increased net returns, feedlot performance, and efficiency, but resulted in carcass yield and quality characteristics that may impact marketing programs.