This episode’s guests were speakers on the Feed Additive to Mitigate Methane Symposium at the ADSA annual meeting.
Episode 191
Recommendations for identification and selection of bioactive compounds to develop antimethanogenic feed additives. Dr. Yáñez-Ruiz (8:23)
To identify molecules that modify how feed ferments in the rumen, researchers have traditionally relied on scientific literature to find plant extracts and compounds that have already been studied. However, advances in computational technology now create new opportunities to model how molecules interact with rumen microbes. After researchers select a candidate compound, they can use in vitro tools to test dose responses before moving into animal experiments.
Recommendations for testing enteric methane-mitigating feed additives in ruminant studies. Dr. Yáñez-Ruiz for Dr. Alexander Hristov (17:07)
After identifying and selecting compounds, researchers must test them in animals. Because these experiments are costly, studies should follow best practices for experimental design, including animal selection, diet formulation, compound delivery, and methane measurement. In addition, many of these practices closely align with regulatory requirements that dictate how in vivo trials must be conducted.
Feed additives for methane mitigation: Modeling the impact of feed additives on enteric methane emission of ruminants—Approaches and recommendations. Dr. Bannink (22:43)
Once researchers collect experimental data, they can use it to develop models that predict an additive’s effectiveness, mode of action, and overall relevance. The goal is to quantify how the additive will perform when fed to an animal. However, this process becomes complex due to variability across datasets and natural fluctuations in animal methane production. Notably, diet type plays a major role in determining additive effectiveness.
A guideline to uncover the mode of action of antimethanogenic feed additives for ruminants. Dr. Belanche (30:03)
Understanding how methane mitigants work remains challenging. Although researchers know that certain compounds reduce methane, they do not always understand how or why these effects occur. Currently, researchers group additives into five main categories based on their mode of action: those that modify rumen fermentation to reduce hydrogen production; methane inhibitors that specifically target methanogens; compounds that inhibit enzymes common to all methanogens; hydrogen sinks that redirect hydrogen toward alternative metabolic pathways; and additives that promote methanotrophs that oxidize methane. Among these, methane inhibitors prove the most effective at reducing emissions, but they do not increase animal productivity. As a result, combining a methane inhibitor with a hydrogen sink may help redirect hydrogen more efficiently and improve productivity outcomes.
Regulations and evidence requirements for the authorization of enteric methane-mitigating feed additives. Dr. Tricarico (41:22)
Regulatory systems vary widely across jurisdictions. Nevertheless, most jurisdictions share two core concepts: regulatory status or legal classification, and intended use. Although every jurisdiction requires a legal classification for feed additives, each uses different criteria to define those classifications. For example, New Zealand recognizes “inhibitor” as a legal classification, while other jurisdictions do not. Additionally, identical terms may carry different meanings depending on the region. Importantly, authorization applies only to the intended use of a compound—not to the compound itself—which makes clarity essential for all stakeholders.
Feed additives for methane mitigation: How to account for the mitigating potential of antimethanogenic feed additives—Approaches and recommendations. Dr. del Prado (49:42)
Finally, a key challenge lies in selecting the appropriate accounting system, whether at the farm level, through lifecycle analysis, within carbon markets, or as part of national greenhouse gas inventories. Each accounting system must align with both the type of experimental data available and the level of complexity required at the chosen scale. Ultimately, experimental data, modeling, and accounting must work together to accurately assess methane mitigation potential.
Panelists share their take-home thoughts. (58:57)
Conclusion
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