Feed Methanogenic Inhibitors
System: Dairy Cattle
Mainly applicable for: Total mixed diets, in zero- or partial-grazing systems. A higher efficacy is observed in systems with high concentrate, starch-rich diets. Low-N diets may benefit from N addition via nitrate.
Not or less applicable for: Nitrate is not applicable for animals that already receive nitrate in the reference situation.
Description
Supplementing methanogenic inhibitors to the feed ration of animals in order to reduce the enteric methane emissions from the rumen and/or intestinal fermentation. The different types of methanogenic inhibitors are listed below. Supplementation should follow recommended dosage and, for some types of inhibitors, also frequent application may be required for an optimal effect. The method of dietary supplementation depends on the type of methanogenic inhibitor that is used, and is important to control the dosage per animal. For nitrate an adaptation period is required (i.e. a gradual, stepwise increase of dietary inclusion up to the target dose) to let the rumen environment adapt to presence of nitrate. Water applications are being developed for grazing systems, or ‘slow release’ formulations that can be offered to animals during milking on farms that have in-shed feeding systems.
Mechanism of effect
The specific mode(s) of action depends on the type of methanogenic inhibitor used. Regarding the inhibitors listed below, 3-nitrooxypropanol (3-NOP) reduces enteric methane emissions directly by binding the enzyme in methanogens as final step in the process of methanogenesis (i.e. production of methane by methanogens). Nitrate also acts to a small extent as an enzyme-inhibitor in methanogens, but mainly acts as a sink of hydrogen when being reduced by micro-organisms to ammonia, leaving less hydrogen substrate for methanogens. As with nitrate nitrogen is added to the ration, ammonia and nitrous oxide emissions from manure storage and application may increase if the ration is not optimized accordingly.
Legend
| ● – Small effect (<5%) | o – No effect |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) |
Effect on total greenhouse gas (GHG) emissions (LCA)
| Mean effect and range in kg CO2-equivalents | per kg product | per farm | |||
| Mean | Min-Max | Mean | Min-Max | Level of evidence | |
| 3-Nitrooxypropanol (3-NOP) | ●● | ● – ●● | ●● | ●–●● | High |
| Nitrate | ●● | ● – ●● | ●● | ●–●● | Medium |
Effect per emission source
| Mean effect on emission from | Manure | Animal | Feed and forage production | Barn & farm inputs | |||
| CH4 | N2O | CH4 | CO2 | N2O | LUC | CO2 | |
| 3-Nitrooxypropanol (3-NOP) | ●●● | ● | |||||
| Nitrate | ● | ●● | ●* | ● | |||
*risk of an adverse effect (see ’cause of variable or unfavourable effect’)
Cause of variable or unfavourable effect
3-Nitrooxypropanol (3-NOP)
The effect on methane increases with a higher dosage of 3-NOP. The effect also is larger with less NDF, less fat and more starch in the diet, such as in low-forage, high-starch diets. The effect is optimal in total mixed rations (TMR), and with non-TMR also depends on feeding method (frequency and amount of additive consumption). Due to differences in rumen conditions, the effect also depends on animal type which hence require their own typical dosages. Additive supplementation should follow recommended dosage and method of delivery for optimal efficacy.
Nitrate
Efficacy of this supplement depends on the dosage, and an animal adaptation period is required (i.e. a stepwise inclusion in the diet to targeted dose). Efficacy does not depend on diet composition, but does depend on animal type due to differences in rumen conditions. At lower feed intake the effect on methane yield (CH4 per kg feed DM) is larger. Increases in ammonia en nitrous oxide emission from manure storage and after manure application should be avoided by adjusting N content of the diet, ensuring N excretion does not increase.
Other Effects
Effects on yield and cost-effectiveness
| Yield animals | crops | Labor time | Costs and revenues Investment | Costs | Revenues | |
| 3-Nitrooxypropanol (3-NOP) | o–● | o | ● | o-● | ●●– ●●● | o |
| Nitrate | o-● | o | ● | o-● | ●●– ●●● | o |
Legend (thresholds differ per indictor and can be found in the tooltip)
| ● – Small favorable effect | o – No effect |
| ●● – Medium favorable effect | ● – Unfavourable effect |
| ●●● – Large favorable effect | ● – ● -Variable effect (depending on farm characteristics or way/level of implementation) |
Effects on other sustainability aspects
| Risks of trade-offs | Potential synergies | |
| 3-Nitrooxypropanol (3-NOP) | Societal or cultural acceptance | – |
| Nitrate | Ammonia emission, animal health | – |
| Literature references | 3-Nitrooxypropanol (3-NOP) |
|---|---|
| Kebreab et al., 2023 | A meta-analysis of effects of 3-nitrooxypropanol on methane production, yield, and intensity in dairy cattle |
| Haisan et al. 2014 | The effects of feeding 3-nitrooxypropanol on methane emissions and productivity of Holstein cows in mid lactation |
| Schilde et al. 2021 | Effects of 3-nitrooxypropanol and varying concentrate feed proportions in the ration on methane emission, rumen fermentation and performance of periparturient dairy cows |
| Reynolds et al., 2014 | Effects of 3-nitrooxypropanol on methane emission, digestion, and energy and nitrogen balance of lactating dairy cows |
| Hristov et al., 2015 | An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production |
| Lopes et al., 2016 | Effect of 3-nitrooxypropanol on methane and hydrogen emissions, methane isotopic signature, and ruminal fermentation in dairy cows |
| Haisan et al., 2016 | The effects of feeding 3-nitrooxypropanol at two doses on milk production, rumen fermentation, plasma metabolites, nutrient digestibility, and methane emissions in lactating Holstein cows |
| Dijkstra et al., 2018 | Short communication: Antimethanogenic effects of 3-nitrooxypropanol depend on supplementation dose, dietary fiber content, and cattle type |
| Wesemael et al., 2019 | Reducing enteric methane emissions from dairy cattle: Two ways to supplement 3-nitrooxypropanol |
| Melgar et al., 2020 | Effects of 3-nitrooxypropanol on rumen fermentation, lactational performance, and resumption of ovarian cyclicity in dairy cows |
| Van Gastelen et al., 2020 | 3-Nitrooxypropanol decreases methane emissions and increases hydrogen emissions of early lactation dairy cows, with associated changes in nutrient digestibility and energy metabolism |
| Melgar et al., 2021 | Enteric methane emission, milk production, and composition of dairy cows fed 3-nitrooxypropanol |
| Kim et al., 2020 | The effects of dietary supplementation with 3-nitrooxypropanol on enteric methane emissions, rumen fermentation, and production performance in ruminants: a meta-analysis |
| Jayanegara et al., 2017 | Use of 3-nitrooxypropanol as feed additive for mitigating enteric methane emissions from ruminants: a meta-analysis |
| Almeida et al., 2021 | Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems |
| Maigaard et al. 2024 | Effects of dietary fat, nitrate, and 3-nitrooxypropanol and their combinations on methane emission, feed intake, and milk production in dairy cows |
| Rivelli et al. 2025 | Efficacy of 3-NOP applied in drinking water on enteric methane reduction in sheep |
| Literature references | Nitrate |
|---|---|
| Zijderveld et al. (2011) | Persistency of methane mitigation by dietary nitrate supplementation in dairy cows |
| Feng et al., 2020 | Antimethanogenic effects of nitrate supplementation in cattle: A meta-analysis |
| Almeida et al., 2021 | Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems |
| Olijhoek et al., 2016 | Effect of dietary nitrate level on enteric methane production, hydrogen emission, rumen fermentation, and nutrient digestibility in dairy cows |
| Petersen et al., 2015 | Dietary nitrate for methane mitigation leads to nitrous oxide emissions from dairy cows |
| Wang et al., 2023 | Effect of nitrate supplementation, dietary protein supply, and genetic yield index on performance, methane emission, and nitrogen efficiency in dairy cows |
| Maigaard et al. 2024 | Effects of dietary fat, nitrate, and 3-nitrooxypropanol and their combinations on methane emission, feed intake, and milk production in dairy cows |