A supplement called 3-nitrooxypropanol (3-NOP) reduces methane emissions from dairy cows by 26% during indoor winter feeding without harming milk production, according to a 2026 study of 88 Irish dairy cows published in the Journal of Dairy Science. Cows receiving the supplement actually produced slightly more protein-rich milk while generating significantly less climate-warming methane gas, making it a practical environmental solution for farms with indoor feeding systems.
Researchers tested a supplement called 3-nitrooxypropanol (3-NOP) on 88 dairy cows to see if it could reduce methane gas they produce while keeping milk production healthy. According to Gram Research analysis, cows that received the supplement produced 26% less methane than cows without it. The treated cows also made slightly more protein-rich milk and didn’t suffer any negative effects on their overall health or milk output. This finding matters because methane from cows contributes to climate change, and this supplement offers a practical way to reduce it during the winter months when cows are indoors eating stored feed.
Key Statistics
A 2026 randomized controlled trial of 88 dairy cows found that supplementing feed with 3-nitrooxypropanol reduced methane emissions by 26% compared to unsupplemented cows, while maintaining normal milk production and improving milk protein content.
According to research published in the Journal of Dairy Science in 2026, cows fed 3-NOP produced 4 times more hydrogen gas and 27% lower methane intensity (methane per kilogram of milk produced) compared to control cows eating standard dairy feed.
A 2026 study of 88 autumn-calving dairy cows showed that 3-NOP supplementation at 71.8 mg per kilogram of feed reduced methane yield by 28% without negatively affecting animal health, body weight, or overall milk production.
Research on 88 Irish dairy cows in 2026 demonstrated that 3-nitrooxypropanol supplementation increased milk protein concentration and milk solids yield while simultaneously cutting methane emissions by more than one-quarter.
The Quick Take
- What they studied: Whether adding a special supplement (3-NOP) to cow feed reduces the methane gas cows burp out while keeping their milk production normal or better
- Who participated: 88 Irish dairy cows (24 first-time mothers and 64 experienced mothers) during their indoor winter feeding period, averaging about 2 months after giving birth
- Key finding: Cows eating the supplement produced 26% less methane and 4 times more hydrogen gas, while making slightly more protein in their milk without any negative side effects
- What it means for you: If you drink dairy milk, this research suggests farms can reduce their environmental impact during winter feeding without changing milk quality or production. However, the supplement doesn’t work well for grazing cows in pasture, so more research is needed for year-round solutions.
The Research Details
Scientists divided 88 dairy cows into two groups: one group ate normal feed (the control group) and the other group ate the same feed plus 3-NOP supplement. The cows lived in a barn and ate a mix of grass silage, corn silage, and grain concentrate. Before collecting data, the researchers watched the cows for 2 weeks to establish a baseline. Then they measured everything for 6 weeks: how much milk each cow produced daily, the milk’s protein and fat content weekly, and the methane gas each cow produced using special equipment called GreenFeed technology.
The researchers carefully matched the two groups before assigning them to treatments. They made sure each group had similar milk production, body weight, and methane output at the start. This matching helps ensure that any differences found were actually caused by the supplement, not by differences between the groups.
This type of study is called a randomized controlled trial, which is considered one of the strongest ways to test whether something actually works. The controlled conditions (cows in a barn eating measured amounts of feed) made it easier to track exactly what the supplement did.
This research approach matters because it tests the supplement under real farm conditions with real dairy cows eating typical Irish winter diets. The controlled barn setting allowed scientists to accurately measure methane using special equipment that would be impossible to use with grazing cows. By measuring multiple outcomes (milk production, milk quality, methane, and cow health), the study shows whether the supplement helps the environment without hurting the farm’s business.
This study has several strengths: it used a large number of cows (88), included both young and experienced mothers to test different groups, measured methane with precise technology rather than estimates, and tracked multiple milk quality measures. The study was published in the Journal of Dairy Science, a respected peer-reviewed journal. One limitation is that it only tested cows indoors during winter—the supplement didn’t work well for grazing cows, so results may not apply to summer grazing systems. The study was relatively short (6 weeks of data collection), so long-term effects remain unknown.
What the Results Show
The main finding was dramatic: cows receiving 3-NOP produced 26% less methane compared to control cows. To put this in perspective, if a control cow produced 100 units of methane, a treated cow produced only 74 units. This reduction happened because the supplement changed how cows digest food in their stomachs, producing hydrogen gas instead of methane.
Importantly, this methane reduction didn’t hurt milk production. Cows on the supplement made about the same amount of milk as control cows. However, the milk quality actually improved slightly: treated cows produced more protein in their milk and more milk solids overall (the valuable parts of milk used to make cheese and yogurt). The supplement also changed the type of fat in the milk, increasing healthier “new” fats made by the cow’s body while decreasing fats from the feed.
The cows’ overall health and body condition remained normal in both groups. They didn’t lose weight, get sick, or show any signs of stress from the supplement. This is crucial because it means farms could use this supplement without worrying about harming their animals.
Hydrogen gas production increased dramatically in treated cows—about 4 times higher than in control cows. This is actually the mechanism by which the supplement works: it redirects the cow’s digestion to produce hydrogen instead of methane. The supplement also improved several milk quality measures: milk protein concentration increased, and the proportion of beneficial fatty acids changed in ways that might be healthier. When researchers calculated methane per unit of milk produced (called methane intensity), the reduction was even more impressive at 27%, showing the supplement makes cows more efficient at converting feed to milk while producing less gas.
This research confirms what smaller previous studies suggested: 3-NOP can reduce methane in dairy cows. However, this study is notable because it tested the supplement on a large group of cows (88 animals) under realistic Irish farm conditions with typical winter diets. Previous research had shown similar methane reductions (20-30%), but this study adds important information about milk quality improvements and confirms the supplement works safely in real farm settings. The study also highlights a gap in previous research: while 3-NOP works indoors, scientists still need to figure out how to make it work for grazing cows during the pasture season.
The study only lasted 6 weeks of data collection, so researchers couldn’t determine if the supplement’s effects continue over months or if cows develop tolerance to it. The research only tested cows indoors eating stored feed during winter—results may differ for grazing cows or different diet types. The study didn’t measure the cost-effectiveness of the supplement or how it might affect farm profitability. Additionally, the supplement didn’t work well for grazing cows (as mentioned in the paper), so farms can’t use it year-round in systems where cows graze pasture. Finally, the study measured methane in a controlled barn setting; real-world farm conditions might produce different results.
The Bottom Line
Based on this research, dairy farms using indoor winter feeding systems could consider 3-NOP supplementation to reduce their methane emissions by about 26%. The supplement appears safe for cows and doesn’t reduce milk production. However, this recommendation applies only to the indoor feeding period (roughly October to April in Ireland). Farms should consult with their veterinarian and nutritionist about cost, proper dosing (71.8 mg per kg of feed), and integration with their specific feeding system. The confidence level for this recommendation is moderate to high for indoor systems but low for grazing systems, where the supplement doesn’t work effectively.
Dairy farmers using indoor winter feeding systems should care about this research, especially those in regions with climate regulations or sustainability goals. Environmental organizations and consumers concerned about climate impact should care because this offers a practical tool to reduce agriculture’s methane footprint. Milk processors and retailers marketing sustainable products might use this information. However, farmers with primarily grazing systems (where cows eat fresh pasture most of the year) should wait for further research, as this supplement doesn’t work well for grazing cows. Individual consumers don’t need to change their milk-buying habits based on this single study.
Methane reduction would begin immediately once cows start eating the supplement—the study measured reduced methane within the first weeks of treatment. However, farms would need to maintain the supplement continuously during the indoor feeding period to see ongoing benefits. If a farm stopped using the supplement, methane production would likely return to normal levels. For environmental impact, the benefits would accumulate over the entire indoor feeding season (typically 6-8 months in Ireland). Farms shouldn’t expect to see changes in milk production or quality for at least 1-2 weeks, as the cow’s digestive system needs time to adjust.
Frequently Asked Questions
Does 3-NOP supplement reduce methane from dairy cows without hurting milk production?
Yes, research shows 3-NOP reduces methane by 26% while maintaining normal milk production and actually improving milk protein content. Cows remained healthy with no negative side effects during the 6-week study period.
How much methane reduction can farms expect from using 3-nitrooxypropanol?
Farms can expect approximately 26-28% reduction in methane emissions when using 3-NOP supplementation at the tested dose of 71.8 mg per kilogram of feed during indoor winter feeding periods.
Does 3-NOP work for grazing cows eating fresh pasture?
The research shows 3-NOP works well for cows indoors eating stored feed but faces challenges with grazing cows. Scientists acknowledge further research is needed to develop effective methane reduction strategies for pasture-based systems.
What happens to milk quality when cows eat 3-NOP supplement?
Milk quality improves slightly: cows produce more protein and milk solids while the type of fat in milk changes to include more beneficial fatty acids. Overall milk production remains unchanged.
How long does it take to see methane reduction after starting 3-NOP supplementation?
Methane reduction begins within the first weeks of supplementation. The study measured reduced emissions after just 6 weeks, suggesting farms could see environmental benefits relatively quickly after implementing the supplement.
Want to Apply This Research?
- Track daily methane reduction percentage for your herd if using 3-NOP supplementation. Set a baseline measurement before starting the supplement, then log weekly average methane emissions (in grams per day) to monitor whether your farm achieves the expected 26% reduction. Compare this metric monthly to ensure consistent results.
- If managing a dairy farm, implement a seasonal protocol: add 3-NOP supplement to your winter feed mix starting when cows move indoors (typically October), maintain consistent dosing at 71.8 mg per kg of dry matter, and discontinue when cows return to pasture grazing. Set calendar reminders for monthly methane monitoring and quarterly reviews with your nutritionist to ensure proper implementation.
- Establish a long-term tracking system that measures methane emissions weekly during the indoor feeding season using on-farm monitoring technology (like GreenFeed). Create a dashboard showing: weekly methane production, methane per kg of milk produced, milk protein percentage, and overall herd health metrics. Compare each year’s winter season to identify trends and optimize supplement timing and dosing.
This research describes findings from a controlled 6-week study on dairy cows in indoor winter feeding systems. Results may not apply to grazing systems, different diets, or different climates. Before implementing 3-NOP supplementation on your farm, consult with a veterinarian and animal nutritionist to ensure proper dosing, safety for your specific herd, and cost-effectiveness. This article is for informational purposes and should not replace professional agricultural or veterinary advice. Individual farm results may vary based on management practices, feed quality, and herd genetics. Long-term effects beyond 6 weeks have not been studied in this research.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.
