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

SIMPLE SUMMARY: Methane is a gas that ruminants naturally release during digestion, and it is a significant contributor to global warming. In efforts to reduce the environmental impact of livestock farming, we explored a red macroalga called Bonnemaisonia hamifera. This macroalga was collected from the shores of Sweden and used in an in vitro digestion experiment to evaluate its effects on ruminal fermentation and methane production from dairy cows. The study examined different inclusion levels of the macroalga in grass silage. We noticed an increase in the proportion of propionate in rumen fluid and a reduction in methane production with inclusion of the macroalga. This is important because reducing methane emissions from ruminants would be beneficial for the environment. B. hamifera exhibited antioxidant properties, which could be beneficial for the animals. In conclusion, this study shows that B. hamifera from Sweden has the potential to make livestock farming more eco-friendly by decreasing methane gas emissions. ABSTRACT: 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.