Reducing Methane Emissions in Dairy Farming: A Literature Review on Feed Additives for Sustainable Livestock Management

Methane (CH₄) emissions from livestock, particularly ruminants, remain a significant environmental concern and a focal point of research in the dairy cattle industry. The agricultural sector, primarily large ruminants, is responsible for more than half of CH₄ emissions in Europe. Given the rapid rise in global temperatures, mitigating enteric methane emissions through dietary interventions is a promising and animal­ friendly approach. Several in vivo studies have investigated the impact of specific feed additives and dietary modifications on CH₄ reduction. Among these, brown algae (Ascophyllum nodosum), red algae (Asparagopsis armata), and 3-nitrooxypropanol have shown potential in mitigating methane emissions. However, the effectiveness and safety of these additives require further evaluation. While red algae supplements have demonstrated an impressive 98 % reduction in CH₄ emissions in in vitro studies, in vivo trials indicate a substantial increase in halogenated hydrocarbon production due to their active compound, bromoform. In contrast, brown algae supplementation, through its production of phlorotannins combined with polyethylene glycol, inhibits methanogens by reducing the growth of certain ciliates, resulting in a 17 % reduction in emitted CH₄. Additionally, 3-nitrooxypropanol supplementation has shown a 16–20 % decrease in CH₄ emissions by blocking the final step of methanogenesis. However, concerns remain regarding the potential development of methanogen resistance to this additive. In conclusion, reducing enteric methane emissions in dairy farming is essential for sustainable livestock management and climate change mitigation. While feed additives such as brown algae, red algae, and 3-nitrooxypropanol show promise, their long­ term efficacy, safety, and potential environmental impacts require further investigation. Continued research is crucial to ensure the development of effective, sustainable, and safe methane mitigation strategies in the dairy industry.