Feed Methanogenic Inhibitors
System: Beef Cattle
Mainly applicable for: For animals in fattening as well as the finishing phase, particularly in total mixed rations. A higher efficacy is observed for low-fiber, high starch diets. Low N rations (or rations with a limiting rumen N balance) may benefit from N addition via nitrate.
Not applicable or effective for: Full grazing systems which do not allow regular consumption of the additive, unless slow-release or water applications become operational.
Description
Supplementing methanogenic inhibitors to the rations in order to reduce enteric methane emission in the rumen. The different types of methanogenic inhibitors are listed below. Supplementation should follow recommended dosage and delivery method 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.
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.
Reference situation
Not feeding methanogenic inhibitors or nitrate.
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). Inclusion of 3-NOP in the diet should follow recommended dose and delivery method for an optimal effect.
Nitrate
The effect on methane increases with a higher dosage. Increases in ammonia and nitrous oxide emissions from manure storage and manure application should be avoided by adjusting N content in the diet, ensuring N excretion does not increase.
| Literature references | 3-Nitrooxypropanol (3-NOP) |
|---|---|
| De Oliviera et al. 2025 (sumitted) | A meta-analysis of 3-nitrooxypropanol effects on methane production and yield in beef cattle |
| Zhang et al. 2021 | Combined effects of 3-nitrooxypropanol and canola oil supplementation on methane emissions, rumen fermentation and biohydrogenation, and total tract digestibility in beef cattle |
| Alemu et al. 2023 | 3-nitrooxypropanol Supplementation of a Forage Diet Decreased Enteric Methane Emissions from Beef Cattle Without Affecting Apparent Total-tract Digestibility |
| Vyas et al. 2018 | The combined effects of supplementing monensin and 3-nitrooxypropanol on methane emissions, growth rate, and feed conversion efficiency in beef cattle fed high-forage and high-grain diets |
| Dijkstra et al., 2018 | Short communication: Antimethanogenic effects of 3-nitrooxypropanol depend on supplementation dose, dietary fiber content, and cattle type |
| Alemu et al. 2023 | 3-Nitrooxypropanol supplementation of a forage diet decreased enteric methane emissions from beef cattle without affecting feed intake and apparent total-tract digestibility |
| Almeida et al., 2023 | Effect of 3-nitrooxypropanol on enteric methane emissions of feedlot cattle fed with a tempered barley-based diet with canola oil |
| 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 |
| Rivelli et al. 2025 | Efficacy of 3-NOP applied in drinking water on enteric methane reduction in sheep |
| Nitrate | |
|---|---|
| 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 |