PS5-23. Mitigation of Enteric Methane Emissions Using a Bromoform-based Feed Additive in Finishing Nellore Cattle.

Abstract The objective of this study was to evaluate the efficacy of a bromoform-based feed additive on enteric methane emissions and animal performance in finishing Nellore cattle fed a typical Brazilian feedlot diet. The experiment was conducted at ESALQ/USP (Piracicaba, Brazil) using 80 Nellore bulls (Bos indicus; 335 ± 19.2 kg BW) allocated to a randomized complete block design with two treatments: CONTROL (total mixed ration; TMR) and ADDITIVE (TMR supplemented with a bromoform-based additive). Animals were individually housed to allow precise measurements of intake and methane emissions. The feeding trial lasted 120 d (36 d adaptation and 84 d treatment). Methane emissions were measured using a GreenFeed system during three measurement periods. Performance variables included dry matter intake (DMI), average daily gain (ADG), and feed efficiency. Data were analyzed using mixed models with treatment as a fixed effect and initial BW as a random block (α = 0.05). The additive substantially reduced methane emissions. Methane production decreased by 50.4%, from 104.6 to 51.9 g CH4/d (P < 0.0001). Methane yield decreased from 12.59 to 6.63 g CH4/kg DMI (P < 0.0001), and methane intensity decreased from 77.18 to 39.55 g CH4/kg ADG (P < 0.0001). Hydrogen production increased from 0.41 to 2.55 g H2/d (P < 0.0001), whereas carbon dioxide production was not affected (P = 0.78). Animal performance was not negatively affected by the additive. Dry matter intake did not differ between treatments (P = 0.267), whereas feed efficiency improved by 5% (P = 0.043), with a tendency for greater ADG (P = 0.081). These results demonstrate that the bromoform-based feed additive is an effective strategy to substantially reduce enteric methane emissions in feedlot Nellore cattle without compromising productivity. Additionally, the improvement in feed efficiency suggests a dual benefit of mitigating the environmental impact of beef production while enhancing production efficiency.