Potential of the Red Macroalga Bonnemaisonia hamifera in Reducing Methane Emissions from Ruminants.

Researchers have been exploring seaweeds to reduce methane (CH ₄ ) emissions from livestock. This study aimed to investigate the potential of a red macroalga, B. hamifera , as an alternative to mitigate CH ₄ emissions. B. hamifera , harvested from the west coast of Sweden, was used in an in vitro experiment using a fully automated gas production system. The experiment was a randomized complete block design consisting of a 48 h incubation that included a control (grass silage) and B. hamifera inclusions at 2.5%, 5.0%, and 7.5% of grass silage OM mixed with buffered rumen fluid. Predicted in vivo CH ₄ production and total gas production were estimated by applying a set of models to the gas production data and in vitro fermentation characteristics were evaluated. The results demonstrated that the inclusion of B. hamifera reduced ( p = 0.01) predicted in vivo CH ₄ and total gas productions, and total gas production linearly decreased ( p = 0.03) with inclusion of B. hamifera . The molar proportion of propionate increased ( p = 0.03) while isovalerate decreased ( p = 0.04) with inclusion of B. hamifera . Chemical analyses revealed that B. hamifera had moderate concentrations of polyphenols. The iodine content was low, and there was no detectable bromoform, suggesting quality advantages over Asparagopsis taxiformis . Additionally, B. hamifera exhibited antioxidant activity similar to Resveratrol. The findings of this study indicated that B. hamifera harvested from temperate waters of Sweden possesses capacity to mitigate CH ₄ in vitro.