3-NOP Feed Additive: Mitigating Climate Change by Reducing Cattle Methane Emissions

Introduction

The global population of ruminants, like dairy and beef cattle, has increased significantly and is expected to keep growing to meet the demand for milk and meat (FAOSTAT, 2017). Billions of microbes (bacteria, protozoa, fungi, and archaea) live in a cow's stomach (rumen) and help digest food (Boone et al., 1993). Methane (CH₄) is produced by archaea using hydrogen (H₂), carbon dioxide (CO₂), methanol, and methylamines from the breakdown of carbohydrates and fats (Pitta et al., 2022). The enteric CH₄ generated during cattle digestion is a potent greenhouse gas (GHG), with a global warming potential 28 times greater than CO₂ over a 100-year period. (Gruninger et al., 2022). Methane emissions from dairy cows are an environmental issue, contributing to climate change (Kebreab et al., 2023) and causing a 2-12% loss of feed energy for the animals (Johnson & Johnson, 1995). Reducing CH₄ emissions from cattle could disrupt microbial fermentation balance, affecting feed intake, digestion, and productivity (Kelly et al., 2019; Pitta et al., 2022). Therefore, researchers have been working on ways to reduce CH₄ emissions without altering feed efficiency and animal productivity. One effective dietary strategy is the use of the feed additive 3-nitrooxypropanol (3-NOP), often marketed as Bovaer®, to mitigate methane emissions in cattle (van Gastelen et al., 2024). 3-NOP works by targeting a specific enzyme (methyl-coenzyme M reductase, MCR) in the methane production pathway in the stomachs of cattle (Duin et al., 2016). Recent studies show that adding 3-NOP to cow feed could potentially reduce methane emissions by:

23 – 37% in dairy cows (Hristov et al., 2015; Haisan et al., 2016; Van Wesemael et al., 2019; Melgar et al., 2020a,b)
27 – 57% in beef cattle (Vyas et al., 2018; Alemu et al., 2021)

In some cases, 3-NOP has been shown to reduce CH₄ emissions by up to 82% (Vyas et al., 2016; McGinn et al., 2019). It is also safe for animals and humans (Yu et al., 2021; Honan et al., 2021). Using 3-NOP in cattle feed is a promising strategy for reducing methane emissions and improving the sustainability of livestock production.

Strategies to Reduce Methane Emissions

Several strategies have been proposed over the years to reduce the environmental impact of ruminant production due to methane emissions. (Hristov et al., 2013; Kebreab et al., 2023; Gadzama 2024). These include:

Improving Animal Genetics, Breeding, and Management: Selective breeding for traits that enhance feed efficiency and reduce methane production.
Improving Animal Health: Ensuring animals are healthy to optimize their productivity and reduce methane emissions.
Improving Forage Quality: Providing high-quality forage to improve digestion and reduce methane emissions.
Using Feed Additives: Adding substances like 3-NOP to the diet to directly reduce methane production.
Diet Reformulation: Adjusting the diet composition to include ingredients that reduce methane emissions.
Rumen Manipulation: Altering the microbial population in the rumen to reduce methane production.
Early Life Programming: Implementing nutritional and management strategies early in life to influence long-term methane production.

Factors Affecting the Efficacy of 3-NOP in Methane Reduction:

Cattle Breed: Dairy cattle show a larger reduction in methane emissions (39%) compared to beef cattle (22%). Among dairy cows, Holstein Friesian cows had a greater reduction (29.6%) compared to Brown Swiss cows (18%) (Ma et al., 2024).
3-NOP Dose: Higher doses of 3-NOP (above 123 mg/kg of dry matter) are more effective in reducing methane emissions (Jayanegara et al., 2018; Dijkstra et al., 2018).
Diet Composition: The type and composition of the diet, as well as dry matter intake, influence the effectiveness of 3-NOP (Dijkstra et al., 2018).
Dietary Fiber: Diets high in fiber reduce the effectiveness of 3-NOP (Dijkstra et al., 2018; Alemu et al., 2021), while high concentrate (grain-based) diets enhance its effectiveness (Romero-Perez et al., 2014; Vyas et al., 2018). Methane reductions of up to 82% have been observed in feedlot cattle on grain-based diets (Vyas et al., 2016). More fiber in the diet lowers 3-NOP's effectiveness by about 1.64% for every 10 g/kg increase in fiber (Dijkstra et al., 2018).
Measurement Methods: Different methods of measuring methane emissions, such as chambers, the sulfur hexafluoride tracer technique, and the GreenFeed system, can cause variability in results.
Duration and Combinations: The duration of 3-NOP supplementation in cattle, whether short-term or long-term, along with its combination with other strategies such as monensin, unsaturated fatty acids, or red algae (Asparagopsis taxiformis), can influence the overall effectiveness. For optimal methane reduction, 3-NOP should be used in high-concentrate diets, which has been shown to significantly lower methane emissions in cattle (Yu et al., 2021).

How does 3-NOP work?

Inhibition of Methane Production: 3-NOP inhibits the enzyme methyl-coenzyme M reductase (MCR), which is crucial for the final step of methane production in the rumen. By blocking this enzyme, 3-NOP effectively reduces the formation of methane (Pitta et al., 2022).
Impact on Rumen Microbes: 3-NOP specifically targets methanogenic archaea, the microbes responsible for methane production. It is particularly effective against certain species like Methanobrevibacter (Pitta et al., 2022).
Hydrogen Redirection: When methane production is inhibited, hydrogen (H₂) accumulates in the rumen. This hydrogen can be redirected to other metabolic pathways, such as the production of volatile fatty acids like propionate, which are beneficial for the animal's energy metabolism (Pitta et al., 2022).
Safety and Efficacy: Studies have shown that 3-NOP is safe for animal consumption and does not negatively affect their overall health or productivity. It reduces methane emissions significantly without harming non-methanogenic bacteria or the animal itself (Yu et al., 2021).

How to Introduce 3-NOP to Cattle

Administering 3-NOP effectively to cattle involves several considerations to ensure optimal methane reduction. Here are the best practices based on current research and guidelines: Mixing into Feed:

Total Mixed Ration (TMR): Mix 3-NOP into the TMR to ensure each animal gets a consistent daily dose. The recommended dosage is 60 – 80 mg of 3-NOP per kilogram of dry matter intake (DMI). The dosage for dairy cows is typically around 60 mg/kg DMI, while beef cattle can range from 100 to 150 mg/kg DMI (USFDA, 2023).
Mineral Feed or Concentrate: If not using TMR, 3-NOP can be included in mineral feed or concentrate feed. The feed should be mixed thoroughly to ensure even distribution (FEFAC, 2023).
Concentrate Pelleting: To ensure it's evenly distributed, and to ensure that each animal receives a consistent dose throughout the day, 3-NOP can be thoroughly mixed into feed during the feed pelleting process. This can lead to consistent methane reduction.

Advantages of Including 3-NOP During Feed Pelleting

Uniform Distribution Pelleting ensures that 3-NOP is evenly distributed throughout the feed, providing a consistent dosage to each animal (Meale et al., 2024). This reduces the risk of uneven intake, which can occur with TMR or concentrate diets (Li et al., 2021).
Enhanced Stability: The pelleting process involves heat, which can enhance the stability of 3-NOP products. This can help maintain its effectiveness in reducing methane emissions over time (Bampidis et al., 2021).
Reduced Feed Sorting: Pelleted feed reduces the ability of animals to sort through their feed, ensuring they consume all components, including 3-NOP (Meale et al., 2024). This is particularly beneficial in preventing selective feeding, which can be an issue with TMR (Van Saun, 2022).
Improved Digestibility: The heat from pelleting partially gelatinizes starch and can denature some anti-nutritional factors, potentially improving the digestibility of the feed (Lancheros et al., 2020; Heydari et al., 2022; Wang et al., 2023).
Convenience and Efficiency: Pelleted feed is easier to handle, store, and transport compared to loose TMR or concentrates (Li et al., 2021). This can lead to labor savings and improved feed management efficiency (Van Saun, 2022).

Storage Recommendation: Store 3-NOP enriched pellets at 4°C or use within two weeks at room temperature to maintain effectiveness (Meale et al., 2024). Therefore, researchers could explore pelleting feed with 3-NOP, which could ensure uniform distribution, enhance stability, reduce feed sorting, improve digestibility, and offer convenience in handling. However, proper mixing, daily feeding, and regular monitoring are key to maintaining its effectiveness in methane reduction.

Conclusion

Studies have demonstrated that 3-NOP begins to reduce methane production within 30 minutes of ingestion and maintains its effectiveness throughout the day. In my next paper, I will explore the impact of dietary 3-NOP as a feed additive on methane reduction in both beef and dairy cattle. Keywords: Methane emissions, 3-Nitrooxypropanol (3-NOP), Bovaer, Dairy cattle, Beef cattle, Greenhouse gas (GHG), Rumen microbes, Feed additive, Climate change, Sustainability

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