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Supplementing with Red Seaweed for Radical Methane Reduction
Sheila Barry, Larry Forero, Josh Davy, and Gaby Maier
Research funded by
RUSSELL L. RUSTICI RANGELAND & CATTLE RESEARCH ENDOWMENT

Red Seaweed & Methane Emission
To date one of the most successful feed additives to reduce methane from beef cattle is the bromoform-containing seaweed, Asparagopsis taxiformis (AT). Research has found that replacing just 0.5% of a cow’s diet on a dry matter basis with AT, or providing bromoform/head/day can reduce the amount of methane from enteric fermentation by as much as 98%. When fed, the Asparagopsis species reduces methanogenic archaea in the rumen thus inhibiting methane production.
This research is providing information on feasibility and efficacy of AT supplementation to producers who manage grazing on California rangeland, creating new opportunities to mitigate enteric methane emissions. AT is being considered a feed additive by the FDA.

Aim
This project aims to assess whether A. taxiformis (red seaweed) can be delivered to grazing cattle via a mineral mix to reduce methane emissions and potentially increase production.
The supplementation trial is being conducted at UC Sierra Foothill Research & Extension Center in Yuba County. Symbrosia, an A. taxiformis producer in Hawaii, is supplying SeaGraze™, a natural A. taxiformis feed additive, for the trial.
Red Seaweed, SeaGraze(TM) additive to be mixed with mineral
Methods and Results
Two groups of stocker cattle grazing rangeland pastures from November 2023 to June 2024 had access to free-choice loose mineral. They consumed approximately 2.0 oz/head/day. SeaGraze™, dried red seaweed was added to the mineral of the treatment group. Treatment cattle consumed 0.24 oz/head/day of SeaGraze™ which provided approx. 100 mg bromoform/head/day.
Treatment cattle consumed less mineral than control during final 45- day period. Over the season (171 days) treatment and control cattle both gained 1.4 lbs per day. Consumption level of mineral was lower than expected for treatment and control. Future research will include Smart Feeders and Green Feeders to measure individual consumption and accurately measure methane.
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