Dietary high-purity tribromoethanol (TBE) supplementation reduces enteric methane emissions in beef cattle

Abstract The livestock industry contributes substantially to global greenhouse gas emissions, with enteric methane (CH4) from ruminants representing a major source. Feed additives that suppress methanogenesis have emerged as promising strategies, provided they do not compromise animal performance. The objective of this study was to evaluate the effects of high-purity 2,2,2-tribromoethanol (TBE) on enteric gas emissions (CH4, CO2, H2), dry matter intake (DMI), average daily gain (ADG), and feed efficiency (FE, ADG/DMI) in beef steers. Twenty-four Red Angus steers (initial body weight (BW) = 477 ± 27 kg) were blocked by BW and randomly assigned to one of three dietary treatments (n = 8 per treatment group): control (0 mg TBE/kg DM), low (15 mg TBE/kg DM), or high (30 mg TBE/kg DM). The TBE was dissolved in canola oil, mixed into a premix, and incorporated into the total mixed ration formulated to meet or exceed National Academies of Sciences, Engineering, and Medicine requirements for finishing beef cattle (ADG, 1.36–1.81 kg/d). The experiment followed a replicated 3 × 3 Latin square design with three 28-d experimental periods, during which treatments were rotated so that each animal received each treatment once. Enteric gas emissions were measured using a GreenFeed system across 8 sampling time points over a 3-day period during the final week of each experimental period. Individual DMI was recorded daily from weighed feed offered and refusals, and BW was measured weekly. Statistical analyses were performed using linear mixed-effects models with treatment and period as fixed effects and animal nested within square as random effects in a repeated measures analysis. Daily TBE supplementation reduced (P < 0.001) CH4 production (g/d) by 15.6% and 32.2% for the low and high treatment groups, respectively, relative to control. Methane yield (g/kg DMI) and intensity (g/kg ADG) were also reduced (P < 0.001 and P = 0.005, respectively) by 10.7% (low) and 28.0% (high), and 12.8% (low) and 33.4% (high), respectively. DMI, ADG, and FE did not differ among treatments. These findings suggest that TBE supplementation can effectively reduce enteric CH4 emissions in beef cattle without adversely affecting feed intake, growth performance, or feed efficiency. Tribromoethanol may therefore represent a potential CH4 mitigation strategy warranting further evaluation regarding long-term efficacy, safety, and practical application in beef production systems.