A feed additive called 3-nitrooxypropanol (3-NOP) reduced methane emissions from dairy cows by 8 percent per day and 9 percent relative to milk production, according to a 2026 randomized controlled trial of 48 cows published in the Journal of Animal Science and Biotechnology. The additive worked without reducing milk production, feed intake, or milk quality, making it a practical option for environmentally conscious dairy farms.
Researchers tested whether a chemical called 3-nitrooxypropanol (3-NOP) could reduce methane gas produced by dairy cows. Methane from cattle contributes to climate change, so finding ways to reduce it matters for the environment. In a 14-week study with 48 cows, scientists found that 3-NOP reduced methane production by 8 percent without hurting milk production or how much cows ate. When combined with beneficial bacteria called direct-fed microbials, the results were similar. This discovery suggests farmers might have a practical tool to make dairy farming more environmentally friendly.
Key Statistics
A 2026 randomized controlled trial of 48 Danish Holstein dairy cows found that 3-nitrooxypropanol supplementation reduced daily methane production by 8 percent and methane intensity by 9 percent without affecting milk yield or feed intake.
According to research reviewed by Gram, even a low dose of 3-NOP at 6.0 mg/kg dry matter successfully reduced methane emissions in dairy cows, suggesting the additive may be cost-effective at lower doses than previously tested.
In a 14-week study of 48 dairy cows, 3-NOP supplementation increased hydrogen gas production, indicating the chemical successfully redirects energy away from methane production toward a non-greenhouse gas alternative.
Direct-fed microbials alone did not reduce methane emissions in the 2026 trial, but when combined with 3-NOP or used alone, they showed a tendency to improve feed efficiency by the end of the 14-week study period.
The Quick Take
- What they studied: Whether a feed additive called 3-NOP could reduce the amount of methane gas that dairy cows produce, and whether combining it with beneficial bacteria would work even better.
- Who participated: Forty-eight Danish Holstein dairy cows (a common breed used for milk production) were divided into four groups and fed different diets over 14 weeks.
- Key finding: Cows that received 3-NOP produced 8 percent less methane gas per day and 9 percent less methane relative to their milk production, without any negative effects on how much they ate or how much milk they produced.
- What it means for you: If you drink dairy milk or eat dairy products, this research suggests farmers may soon have an affordable way to reduce the environmental impact of dairy farming. The additive appears safe and doesn’t reduce milk production, making it practical for real farms.
The Research Details
Scientists conducted a randomized controlled trial, which is considered one of the strongest types of research. They took 48 dairy cows and randomly assigned them to four different diet groups. One group ate a normal control diet, while the other three groups received the same diet plus either 3-NOP (a chemical that blocks methane production), beneficial bacteria called direct-fed microbials, or both additives combined. The cows ate these diets for 14 weeks while researchers measured how much methane they produced, how much they ate, and how much milk they made.
The researchers measured methane in two ways: total methane production per day and methane intensity, which compares methane to milk produced. They also collected samples from inside the cows’ mouths to study the bacteria living there, since these bacteria are involved in methane production. This approach allowed them to see both the practical effects (less methane, same milk) and the biological changes happening inside the cows.
This study design is important because it controls for other factors that might affect results. By randomly assigning cows to groups and keeping everything else the same, researchers can be confident that any differences they see are actually caused by the feed additives, not by other variables. Testing both the additive alone and combined with bacteria helps show whether the combination works better than either one by itself.
This study has several strengths: it used a randomized design with a control group, included a reasonable number of cows (48), and lasted long enough (14 weeks) to see real effects. However, the researchers note that 3-NOP was accidentally included at a lower dose than planned due to a mixing error, which actually makes the results more impressive since even the lower dose worked. The study was conducted in Denmark with one breed of cow, so results might vary in other countries or with different breeds. The study was published in a peer-reviewed scientific journal, meaning other experts reviewed it before publication.
What the Results Show
The main finding was that 3-NOP successfully reduced methane emissions. Cows receiving 3-NOP produced 8 percent less methane per day compared to control cows. When researchers looked at methane intensity (methane per unit of milk produced), the reduction was even larger at 9 percent. Importantly, this reduction happened without any negative effects on the cows. The cows that received 3-NOP ate the same amount of food, produced the same amount of milk, and maintained the same milk quality as control cows.
Interestingly, the 3-NOP treatment increased hydrogen gas production in the cows. This is actually a good sign because it suggests the chemical is working as intended: it’s blocking one pathway for methane production, and the cows’ digestive systems are releasing the energy as hydrogen instead. This hydrogen is not a greenhouse gas like methane, so this is an environmentally beneficial shift.
When researchers looked at the bacteria in the cows’ mouths, they found that 3-NOP increased certain bacterial groups called Megasphaera and Prevotella. These changes in the bacterial community help explain how 3-NOP reduces methane at the biological level.
The direct-fed microbials (beneficial bacteria) alone did not significantly reduce methane emissions. However, they did show some interesting effects: they reduced how much of the mixed feed cows ate at the beginning of the study, which temporarily lowered milk production in weeks 3 to 8. But these negative effects disappeared over time, and by the end of the 14-week study, cows receiving the bacteria showed slightly improved feed efficiency (they produced more milk per unit of food eaten).
When 3-NOP and direct-fed microbials were combined, the results were similar to 3-NOP alone for methane reduction. The combination did not provide additional benefits beyond what 3-NOP achieved by itself. The direct-fed microbials changed the bacterial community in the cows’ mouths, particularly increasing bacteria from the Lactobacillaceae family, especially in the later weeks of the study. This suggests the beneficial bacteria were establishing themselves in the cows’ digestive systems over time.
According to Gram Research analysis, this study confirms what previous research has suggested about 3-NOP: it is an effective methane reducer. However, this is one of the first studies to test such a low dose of 3-NOP (6.0 mg/kg dry matter), and it still worked, which is encouraging for cost-effectiveness. Previous studies on direct-fed microbials have shown mixed results, and this study’s finding that they don’t directly reduce methane aligns with some earlier research. The temporary reduction in feed intake from the bacteria is a new finding that suggests timing and adaptation may matter when introducing these supplements.
The most important limitation is that 3-NOP was accidentally included at a lower dose than intended due to a mixing error. While this makes the results more impressive (the lower dose still worked), it means we don’t know how well the standard dose would perform. The study was conducted only in Denmark with one breed of dairy cow (Holstein), so results might differ in other countries or with different breeds. The study lasted 14 weeks, which is a reasonable timeframe but relatively short for long-term effects. The researchers did not measure whether the methane reduction would persist if farmers stopped using the additive. Finally, this study measured methane in controlled research settings, so real-world results on commercial farms might vary slightly.
The Bottom Line
Based on this research, 3-NOP appears to be a safe and effective feed additive for reducing methane emissions from dairy cows. The evidence is strong (high confidence) that it reduces methane without harming milk production or cow health. Direct-fed microbials alone do not reduce methane but may improve feed efficiency over time, though the evidence is weaker (moderate confidence). Farmers considering these additives should consult with their veterinarian or nutritionist about cost, availability, and how to introduce them properly to their herds.
Dairy farmers should care about this research because it offers a practical tool to reduce their environmental impact without sacrificing milk production or profitability. Environmental advocates and consumers concerned about climate change should care because reducing methane from cattle is one strategy to address agricultural greenhouse gas emissions. Policymakers considering regulations on agricultural emissions should consider that effective, practical solutions like 3-NOP already exist. People with no connection to dairy farming may care less about the immediate applications but should understand that agriculture contributes to climate change and that science-based solutions are being developed.
The methane reduction from 3-NOP appears to happen quickly. In this study, researchers measured the effects over 14 weeks and saw consistent results throughout. Farmers could likely expect to see reduced methane emissions within weeks of starting the additive, assuming they introduce it properly. The effects on bacterial communities took longer to develop, with some changes more apparent in later weeks, but this doesn’t affect the practical methane reduction benefits.
Frequently Asked Questions
Does 3-NOP reduce methane from dairy cows without affecting milk production?
Yes, a 2026 trial of 48 cows found that 3-NOP reduced methane by 8 to 9 percent while maintaining identical milk yield, composition, and feed intake compared to control cows.
How much does methane from dairy farming contribute to climate change?
Cattle produce significant methane through their digestive process, and methane is a potent greenhouse gas. Reducing methane from dairy cows is considered an important strategy for lowering agricultural emissions and addressing climate change.
Can direct-fed microbials reduce methane in cows?
In this 2026 study, direct-fed microbials alone did not reduce methane emissions. However, they showed some promise for improving feed efficiency over time, though effects were modest.
Is 3-NOP safe for dairy cows and does it affect milk safety?
The 2026 trial found no negative effects on cow health, milk yield, or milk composition from 3-NOP supplementation, suggesting it is safe for dairy cows and does not compromise milk quality.
How quickly does 3-NOP start reducing methane in cows?
The 2026 study measured consistent methane reduction throughout the 14-week trial, suggesting 3-NOP begins working relatively quickly, likely within weeks of supplementation starting.
Want to Apply This Research?
- Track weekly methane emissions per cow (if using farm monitoring equipment) or monitor milk production and feed intake to ensure the additive isn’t negatively affecting herd performance. Record the date 3-NOP supplementation begins and note any changes in cow behavior or milk quality.
- If you manage a dairy farm, implement 3-NOP supplementation in your feed program by working with your feed supplier and veterinarian to source the additive and determine proper dosing for your herd size. Start with a subset of cows if you want to pilot the program before full implementation.
- Establish a baseline of your current methane emissions and milk production metrics before adding 3-NOP. Then measure the same metrics weekly or monthly for at least 8 to 12 weeks to confirm the additive is working as expected in your specific operation. Track feed costs and milk revenue to ensure the investment in the additive is economically worthwhile.
This research describes the effects of 3-nitrooxypropanol and direct-fed microbials in a controlled research setting with 48 dairy cows over 14 weeks. Results may vary based on cow breed, farm conditions, feed type, and climate. Before implementing any feed additive, consult with a veterinarian, animal nutritionist, or your feed supplier to determine appropriate dosing, sourcing, and integration into your specific herd management system. This article is for informational purposes and should not replace professional agricultural or veterinary advice. The accidental low dose of 3-NOP used in this study means results at standard recommended doses may differ.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.