A resolution in the California Legislature aims to establish a thoughtful, principled framework to address the state’s largest agricultural greenhouse gas emissions source: enteric methane from livestock. Senate Joint Resolution 5 (SJR 5), authored by Senator Josh Becker, calls for greater state and federal support to evaluate and accelerate the adoption of enteric methane-reducing strategies. The resolution affirms the Legislature’s support for advancing approaches that lower emissions while sustaining the economic viability of California’s cattle industries. It emphasizes that the government should pursue voluntary enteric solutions that are part of a broader strategy that balances environmental progress with market realities and consumer trust. If passed, the Senate would also formally transmit the resolution to federal lawmakers, calling on Congress to support enteric solutions at the national level. CalCAN worked closely with our dairy partners and Senator Becker’s office to ensure that the nonbinding resolution highlights both the potential and limitations of currently existing enteric solutions, while prioritizing farmer viability and equitable access in future policy development.

Background

Since the state set a goal to reduce dairy and livestock methane emissions by 40% by 2030, there has been increased interest in enteric methane, a byproduct of digestion in ruminant animals, e.g., cows, sheep, and goats. Microbes in the rumen of an animal’s stomach break down feed through fermentation and produce methane, which is expelled primarily through belching. According to the California Air Resources Board (CARB), livestock accounts for about 70% of the state’s agricultural greenhouse gas emissions, or approximately 20.9 million metric tons of carbon dioxide equivalent (CO₂e). About 11 million metric tons come from enteric fermentation. The remainder is primarily attributed to methane emissions from anaerobic manure storage.

The 2023–2024 state budget allocated $10 million to initiate an enteric methane incentive program, but to date, the California Department of Food and Agriculture (CDFA) has reserved these funds for research grants due to the limited availability of proven solutions.

Federal attention is also growing. In May 2024, the U.S. Food and Drug Administration (FDA) approved the feed additive Bovaer, developed by Dutch company DSM, as a safe “livestock drug”, marking the first time the agency has assessed and accepted a product’s enteric methane reduction claims. Bovear contains the synthetic organic chemical 3-nitrooxypropanol (3-NOP), and pharmecutical company pharmaceutical company Elanco has exclusive rights for marketing it in the U.S. Later in 2024, the USDA announced over $114 million through the Regional Conservation Partnership Program to fund pilot projects of using Bovear on commercial beef and dairy operations, including almost $20 million for California-based projects.

Reflecting the growing momentum around enteric methane solutions, CDFA and the UC Davis College of Agricultural and Environmental Sciences hosted the third annual State of the Science Summit last week. Although the summit covered methane emissions broadly, much of the discussion focused on the latest science, technologies, investment trends, and policy developments related to enteric methane. CalCAN participated alongside attendees from 11 countries to explore the opportunities, challenges, and complexities of addressing enteric emissions. Speakers and panelists brought a wide range of perspectives—some expressed enthusiasm over recent progress and near-term potential, while others emphasized the need for continued research and deliberation. Some attendees also raised concerns over how enteric efforts will include small-scale and pasture-based producers, especially in developing countries, where most of the world’s ruminant livestock live.

Overview of Enteric Methane Strategies

In the remainder of this blog, we summarize current scientific findings on leading strategies for reducing enteric methane and assess their effectiveness, trade-offs, and limitations. While innovations are emerging rapidly, reflected in the wide range of startup ventures, initiatives, and interventions featured at the 2025 State of the Science Summit, this overview focuses on the most relevant developments for California’s dairy and livestock sectors in the near term. We also consider how efforts to reduce enteric methane can align with broader priorities, including farm viability, life cycle impacts, and equity for small-scale, organic, and pasture-based producers. Given the remaining scientific and practical uncertainties, we call on state and federal government efforts addressing dairy and livestock methane to prioritize support for the existing and proven-effective practices funded by the Alternative Manure Management Program.

Feed Additives Under Development

(a) 3-nitrooxypropanol (3-NOP)

3-NOP is a flavorless, odorless chemical feed additive that targets inhibiting the enzyme in the animal’s rumen responsible for methane formation. Studies have found that the average methane reductions of 3-NOP range from 27 to 35%, depending on the level of concentrations in the animal’s diet and other factors such as fiber and dietary fat levels. 

However, 3-NOP is not approved for certified organic operations in the US, and various barriers remain to widespread adoption. The economic feasibility of the product varies. Some of the research on 3-NOP has backed up DSM’s claims that 3-NOP can improve feed efficiency and/or milk yields (in dairy). However, a 2025 U.S.-based study that analyzed data from 15 other studies on dairy cows found that supplementation with 3-NOP resulted in an average daily loss of $0.35 per cow due to reduced dry matter intake and slight decreases in milk yield. Even when 3-NOP achieves improved efficiency or production, it will not fully offset the farmer’s costs of purchasing 3-NOP, so voluntary adoption is unlikely without incentives. The 2025 study found that cost neutrality would require payments of $0.21 to $0.42 per cow per day, with an average annual cost of $128,000 for a dairy with 1,000 milking cows.  Another study found that CO₂e needs to be priced at $109/tonne to maintain a neutral net return for farmers from 3-NOP supplementation. Furthermore, the UK saw a consumer backlash against milk from dairies using 3-NOP over social media, raising questions about widespread consumer acceptance.

(b) Red Seaweed (Asparagopsis taxiformis)

Another additive drawing significant attention is red seaweed, specifically Asparagopsis taxiformis, which contains bromoform, a compound that can disrupt methane production in the rumen. Certified dairy and livestock operations can use red seaweed feed and water additives. U.S. studies have shown over 80% enteric reductions in feedlot beef trials, 40% in grazing beef cattle, and over 50% in dairy cows without negative impact on animal or human health. A trial on Straus Organic Dairy Farm in west Marin achieved average reductions of 52% and as high as 92%. However, the solution has not been as well-studied as 3-NOP. At least one study on dairy cows outside the US indicated that the methane reduction effectiveness of red seaweed disappeared after a few months, showing that more research will help better understand the impacts of red seaweeds under different conditions. 

In 2022, CDFA approved a red seaweed product produced by Hawaii-based Blue Ocean Barns,  but registered it as a “livestock drug,” requiring FDA approval before the company can sell it as a feed ingredient in California. During the Biden Administration, the FDA began to work with companies and Congress to approve feed additives like red seaweed that work “within the gut of the affected animal,” and was working with Congress to clarify regulatory pathways. The Innovative Feed Act, if passed, would streamline the approval process. However, it is unclear whether efforts at the FDA will continue under the new administration. 

Meanwhile, other seaweed production companies are emerging in Australia, Europe, and the Americas, seeking to commercialize Asparagopsis for livestock. However, large-scale production raises important environmental and logistical concerns. For example, a Swedish life cycle assessment found that land-based cultivation of red seaweed requires high inputs of salt, water, and thermal energy, especially in cooler climates where energy demand increases. If seaweed production uses fossil fuels to meet these energy needs, it could partially offset the methane reductions achieved through feed supplementation.

(c) Existing Organic Feed Options and Potential Future Developments 

Not all methane-reducing feed additives require FDA approval. Some compounds, such as essential oil blends or plant-derived additives, are classified as Generally Recognized as Safe (GRAS), meaning they can be marketed without premarket approval for feed use, though the FDA has not evaluated their methane reduction claims. 

Two prominent examples are Agolin® Ruminant and Mootral® Ruminant. Studies show Agolin can reduce emissions from around 10% ( dairy) to 20% (beef steers) and increase milk yields by about 4%. Mootral can mitigate enteric methane emissions, but more research is needed to show whether the reductions are consistent. 

A 2024 California study found that feeding dairy cows grape pomace, a byproduct of the state’s wine industry, reduced methane emissions by 10-11%. Other organic options, such as lemongrass and curry leaves, have shown some efficacy in early trials, though more work is needed to validate their impact across diets and environments.

There are other emerging technologies that have varying levels of proven effectiveness, are not organic, and do not yet have FDA approval, including several synthetic chemical feed additives and a genetically engineered oral treatment that alters the genes of the animal’s microbial systems in their rumen. 

Non-Feed Additive Solutions:  Feed Management, Genetic Selection, Vaccines   

Some experts at the 2025 State of the Science Summit proposed diet reformulation as the best path forward for reducing enteric emissions in developing countries.  Adjusting rations to better match nutritional requirements can reduce CH₄ emissions per unit of product. However, the potential for additional improvements is less clear in intensive systems, such as those in the United States, where diets are already optimized. Furthermore, increasing the use of feed crops and concentrates in diets can lead to higher CO₂ and N₂O emissions from expanded crop production, fertilizer use, soil carbon loss due to pasture conversion, and changes in manure composition that may increase the release of other greenhouse gases. These trade-offs, along with high costs and limited feasibility in many regions, underscore the need for caution and consideration of full life cycle impacts. 

Improving livestock productivity through breeding has historically reduced methane emissions per unit of milk production by increasing feed conversion efficiency. However, further increases in milk production will offer diminishing returns in methane reduction efficiency, suggesting the need for breeding specifically for methane-efficient cows. Genetic variability and heritability of methane emission traits in cattle have been demonstrated, suggesting achievable methane reductions through selective breeding. A 2022 Dutch study found that selective breeding could reduce the emissions intensity of dairy cattle by an average of 1% per year, reaching 24% by 2050. At the 2025 State of the Science Summit, several voiced the opinion that breeding may have the most potential of enteric solutions. Overall, dietary reformulation and feed additive inclusion provide immediate and reversible effects, while selective breeding produces lasting, cumulative CH4 emission reductions. However, selecting exclusively for low-methane cows could negatively impact fiber digestion and rumen function, emphasizing the need for a balanced multi-trait selection approach. 

Several startup companies are developing vaccines that stimulate an animal’s immune system to produce antibodies that are secreted in saliva and transported to the rumen, where they bind to methanogens and impair their metabolism, reducing methane formation. However, panelists at the 2025 State of the Science Summit pointed out that enteric vaccines face regulatory hurdles and their pathway to market in the United States is unclear. 

Grazing and Forage Strategies: Limited Research, Promising Pathways

Methane mitigation research has overwhelmingly focused on confined animal systems, leaving a gap in data and strategies for grazing operations.

Some evidence suggests that prescribed and rotational grazing practices (sometimes referred to as regenerative grazing) can help lower enteric methane emissions, which are often higher in grazing systems due to higher fiber diets. Rotating livestock before they take a “second bite” maximizes the accumulation of carbon in the roots and shoots and leads to less fibrous and more energy-dense forage, which can reduce methane production in grazing animals. Other studies have emphasized that grazing intensity, pre-grazing herbage mass, and forage maturity all influence enteric methane outcomes. For example, one study found that steers grazing a cover crop mix of vetch, ryegrass, and forage radish produced 36% less methane per unit of energy intake and 29% less total methane than those on standard legume–grass pastures. However, results are highly context-dependent, and long-term, controlled studies in real-world grazing systems are rare. Researchers also argue that evaluation of enteric strategies in grazing systems should use full life cycle assessments that account not just for methane emissions but also for soil carbon sequestration, forage productivity, and other ecosystem services. As a result, it’s challenging to draw universal conclusions. 

At the 2025 State of the Science Summit, a Minnesota State University researcher emphasized that the scientific literature showed that adaptive grazing was more efficient per unit of methane production at producing beef than conventional grazing. Furthermore, ongoing research across the country in which he is involved has monitored that adaptive grazing, in particular, is highly effective at sequestering CO2, suggesting that there should be greater consideration of adaptive grazing in discussions on enteric solutions. Similarly, a 2020 study in Canada found that adaptive grazing not only increases soil carbon sequestration but also methane sequestration.

Barriers to Enteric Solutions and Recommendations for Effective, Equitable Dairy and Livestock Methane Policy 

Economic feasibility remains one of the most significant barriers to widespread adoption of enteric methane-reducing feed additives like 3-NOP. A 2024 study analyzing U.S. feedlot producer behavior found that adoption decisions hinge on whether financial incentives or returns offset costs. However, the study also revealed that large operations—those finishing more than 2,000 head per year—required far smaller financial incentives to adopt 3-NOP than small operations, underscoring a structural equity challenge. For example, with 3-NOP priced at $0.25 per head per day, large producers needed only about $3.26 per hundredweight in added revenue to break even, while small producers required more than twice that amount. Additionally, without careful policy design, most public or private funding is likely to flow to the largest operations. In one modeled scenario, more than 90% of a hypothetical $800 million incentive program would go to fewer than 750 large feedlots (receiving an average of $ 1 million each annually), leaving small and mid-sized producers with a fraction of the support (receiving an average of $10,500 annually). 

Operational fit is another challenge. Many enteric feed additives—especially those like 3-NOP that require daily, precise dosing—are best suited for large confinement systems that mix their own feed on site. That limits their accessibility to smaller and mid-sized operations that purchase feed pre-mixed from feed mills and organic and pasture-based producers more often.

Without practical and cost-effective options for all scales and types of dairy and livestock operations, enteric methane reduction strategies risk excluding the producers already underserved by California’s dairy methane incentives programs, namely small and medium-scale, organic, and pasture-based operations. Senator Becker’s Senate Joint Resolution 5 provides a solid framework for guiding the needed investments in research and thoughtful planning required to develop an effective and equitable enteric strategy. 

As California explores enteric methane mitigation strategies, policy design must reflect scientific effectiveness, feasibility, equity, and long-term sustainability. Meanwhile, it is crucial that the state increases funding for the Alternative Manure Management Program, which has a proven track record as an accessible solution for mitigating manure methane emissions in small-scale, organic, and pastured dairies, while delivering significant co-benefits.