Mitigating methane emissions in grazing beef cattle with a seaweed-based feed additive: Implications for...

The ruminant livestock sector considerably contributes to global greenhouse gas emissions. This study investigates the effectiveness of pelleted bromoform-containing seaweed (Asparagopsis taxiformis) (Brominata) as an enteric methane (CH₄) inhibitor in grazing beef cattle. The primary objective was to assess the impact of this antimethanogenic additive on enteric CH₄ emissions under real-world farm conditions. Twenty-four beef steers, crossbreeds of Wagyu and Angus, with an average liveweight of 399 ± 21.7 kg, were allocated to two treatment groups: Control and Brominata. These animals underwent regular weigh-ins every 14 d, and measurements of CH₄, carbon dioxide (CO₂), and hydrogen (H₂) emissions were conducted using the GreenFeed system. Statistical analysis was conducted using SAS 9.4, wherein the model incorporated fixed effects for treatment, time, their interaction, and a covariate, while accounting for animal variations as a random effect within each phase. Three phases of bromoform intake were identified: a 3-wk ramp-up phase, a 3-wk optimal phase, and a 2-wk decreasing phase. No differences were observed between the weekly initial and final liveweight, average daily gain, and predicted dry matter intake. During optimal and decreasing phases, average enteric CH₄ emissions were significantly reduced in steers that received Brominata supplementation compared to those without supplementation (115 vs. 185 g/d, respectively). Additionally, both groups had similar CO₂ emissions (6.8 vs. 7.2 kg/d), while H₂ emissions were lower in the control group (3.4 vs. 1.8 g/d). The findings suggest that pelleted bromoform-containing feed additive has the potential to reduce enteric CH₄ emissions from grazing beef cattle.