Ration additions have the potential to reduce enteric methane emissions released by ruminants.

We can see the world as it is or as we wish it were. The truth is ruminants are greenhouse gas emitters. They emit greenhouse gases via belching methane and carbon dioxide and through manure excretion of methane and nitrous oxide. When added together, the U.S. dairy industry releases 99.7 million metric tons of carbon dioxide equivalents (CO2eq), which is about 1.6% of total U.S. emissions.

Dairy’s footprint is small on a relative scale, but it’s important to remember the sheer volume of U.S. greenhouse gas emissions. Globally, the U.S. ranks second in total emissions, with approximately 6 billion metric tons emitted on an annual basis. China emits 16 billion tons of CO2eq annually and is by far the world leader in emissions.

The U.S. dairy greenhouse gas footprint is larger than whole countries such as Peru, New Zealand, Norway, and Ireland, just to name a few. So, although U.S. dairy is a small share of the total U.S. emissions footprint, it still has a substantial carbon footprint that warrants our attention. Being a small share of emissions doesn’t remove the responsibility to manage it. Proactive management, as U.S. dairy is doing, makes us a responsible and reliable supply chain partner.

Redirecting energy

Reducing our carbon footprint can mean improved efficiency and profitability over the long term. The science is still developing, but there is some evidence that reducing methane emissions may reroute some energy toward milkfat in some cases. Much more needs to be done to capture the energy from methane reductions for productive purposes to enhance farmer profitability.

Additionally, there is still ongoing investment in reducing emissions from dairy farms. A report from climate auditing group PwC noted that 84% of companies with emissions reduction commitments maintained or augmented their commitments while 83% invested in low-carbon research and development investments. An Economist analysis also demonstrated these commitments matter, as companies with emissions reduction commitments had double the emissions reductions of their peers. Even though discourse and sentiment may have shifted, the money still shows that reducing the footprint of emissions remains a consumer and business priority.

Updates in the feed additives

The amount, rigor, and pace of new data on the various nutritional tools that can mitigate enteric methane emission from ruminants has been impressive. As new data comes out, it’s critical to refresh our understanding of what tools work, how well they work, and any nuance related to the latter. We’ll briefly discuss updates from the scientific community over the past couple years regarding feed additive opportunities.

3-nitrooxypropanol (3NOP): 3NOP is probably the most rigorously analyzed methane-mitigating feed additive. Multiple meta-analyses have been published on its efficacy in reducing methane – supplementing 3NOP in the ration reduces methane emissions from dairy cattle by about 30%.

What other effects does it have? So far, recent meta-analyses have indicated that 3NOP reduces dry matter intake by about 3.5%, while energy-corrected milk yield was not significantly affected, although the mean response was -1.5%. Interestingly, providing 3NOP increases milkfat and protein concentration. There is additional ongoing research across a variety of institutions investigating the effects of 3NOP, so there is more data to come. This means the story may still change on how to best implement this tool on farms.

Seaweed and bromoform: One of the other giants in the methane space, at least relative to its potential for methane mitigation, is seaweed and its active compound, bromoform. A University of California-Davis group conducted a meta-analysis on bromoform-containing feed ingredients to evaluate its effects on methane emissions and animal performance. They observed that providing bromoform at an average dose of 25 milligrams per kilogram (mg/kg) of dry matter reduced enteric methane by 47%. The effect was enhanced with higher doses of bromoform. Unfortunately, they also observed reductions in feed intake and milk yield of 6% and 5%, respectively.

The use of bromoform-containing feed ingredients includes risks for both human and animal health. Mitigation of the risks is necessary prior to widespread adoption of bromoform-containing feed ingredients.

Essential oils: One additional category of methane-mitigating feed additives is essential oils, or more simply, plant-derived compounds that modulate rumen metabolism. One of the more researched blends contains geranyl acetate and eugenol. A 2020 analysis suggested it can reduce methane by approximately 10%.

Recent research conducted in North America under different dietary scenarios reveals a more nuanced picture. One study from Pennsylvania State University did not observe methane reductions when providing the essential oil blend, but milkfat production improved by 8%. Another experiment demonstrated that providing the essential oils did not affect milk production or methane emissions. The authors acknowledged that we need to understand how some compounds and additives work in different types of rations.

There is also research on other compounds like capsicum oleoresin, cinnamaldehyde, and oregano, which yielded varying results. Certainly, more needs to be done to understand when these plant-derived compounds are helpful and when they are not.

The right tools

The bottom line is that the U.S. dairyindustry contributes greenhouse gases to the atmosphere. We have tools that substantially reduce part of that footprint — the enteric methane that cows belch out from their rumen. 3NOP reduces methane with minimal effects on animal performance while bromoform-containing compounds reduce methane but also reduce feed intake and milk yield. The use of essential oils has some promise, but the variety of compounds and inconsistent responses make effective implementation on farms a challenge.

When implementing any of these solutions, economics obviously need to be considered. Fortunately, there are two calculators for producers and nutritionists to use. Use these tools to objectively evaluate what makes sense for your farm.