Expert Insight: Reducing the carbon footprint of dairying 

By Dr Nial O’Boyle, CattleEye Product Director & Veterinarian

“There are known knowns… there are known unknowns… but there are also unknown unknowns.”
Donald Rumsfeld

This famous quote, originally about military intelligence, can aptly frame the challenge of reducing methane and carbon emissions in dairy farming. 

In tackling dairy cows’ greenhouse gas output, we have: 

• known knowns – proven strategies that we know cut emissions. 
• known unknowns – emerging solutions that are being explored but whose full impacts we know we don’t know yet. 
• unknown unknowns – innovations not yet on our radar that could further transform dairy sustainability. 

Known Knowns: Proven practices to reduce emissions

By keeping dairy cows healthier and more productive, these practices reduce wasted resources and methane output. Three areas stand out as “known knowns” in emission reduction:

Optimising cow health and body condition

Healthy cows produce milk more efficiently, which means fewer emissions per litre of milk. Managing body condition score (BCS), ensuring cows are neither too thin nor over-conditioned, is vital for herd health. Preventing metabolic illnesses through good nutrition and body condition management means more milk from the same inputs, cutting the carbon footprint of each litre produced. 

Healthier cows emit less methane per unit of milk because they convert feed to milk more effectively. Common diseases like mastitis, reproductive issues, or lameness all drag down efficiency. A recent review quantified this – each case of mastitis or lameness can raise a cow’s greenhouse gas emissions per unit of milk by roughly 7–8%, and fertility problems by up to 16% (Džermeikaitė et al. 2024). Up until now BCS has been extremely difficult to do objectively on a consistent basis, but CattleEye’s machine vision enables actionable data to be produced objectively and frequently, unlocking new ways to proactively manage body condition.  

Improving longevity

Perhaps the biggest “known known” opportunity is to simply let cows live longer, more productive lives. Increasing cow longevity dramatically lowers the carbon footprint per unit of milk. When a cow stays in the herd for more lactations, the overhead cost of rearing a replacement (and the unproductive growth period of a heifer) is spread out over more milk. In contrast, a cow that leaves the herd after only one lactation carries the climate burden of raising a calf and heifer that barely produced milk before culling.

Modelling studies illustrate that a cow that completes 5 instead of 3 lactations had up to 40% lower greenhouse gas emissions per kilogram of milk over their lifetime (von Soosten et al. 2020). 

Early detection and treatment of lameness

Lameness in dairy cows is a well-recognised problem for animal welfare and farm productivity, and it is a climate problem too. Lame cows produce less milk and are more likely to be culled earlier, which undermines the efficiency of milk production. Unfortunately, about 1-in-3 dairy cows are lame at any one time. An Irish study indicated that lameness could account for 7-9% of on farm environmental impacts (Chen et al. 2016). 

Early detection and intervention are key to managing lameness. Traditionally, farmers rely on visual locomotion scoring, but this can be labour-intensive and inconsistent. Innovative AI-systems (such as CattleEye ) can automatically monitor cows’ gait every day. CattleEye has been academically validated, achieving mobility scores highly consistent with expert veterinarians, (Siachos et al, 2025). This early detection allows for EDPET (early detection prompt effective treatment), a cornerstone of lameness management. 

Known Unknowns: Promising but uncertain solutions

Beyond the well-understood practices above, the dairy industry is experimenting with a range of new approaches to cut methane emissions. These are the “known unknowns” – we know these ideas could help, but we’re still learning how effective they truly are, what trade-offs they entail, and how to implement them practically at scale.

Rumen additives are a prime example. In recent years, scientists have tested feed supplements that can inhibit methane-producing microbes in the cow’s rumen (the gut fermenters called methanogens). These methane reduction prediction numbers are exciting, and these additives are often touted as climate “game changers” for livestock.

However, the real-world uncertainty around these interventions is significant. It’s one thing to examine a new additive in a controlled trial; it’s another to reliably administer it to millions of cows on diverse farms without unintended consequences. Open questions remain about long-term efficacy (will methanogens adapt, or methane reductions taper off over time?), animal health and productivity (some trials noted slight changes in feed intake or weight gain when methane was suppressed, and economic feasibility (who will pay for these supplements, and do they pay for themselves via improved efficiency?). Regulatory approvals are also a hurdle, and some may face feed safety and supply chain challenges. Early indications are that these tools can be part of the solution, but they should complement, not replace, the basic herd management practices already known to reduce emissions.

Other “known unknown” approaches include genetic selection and vaccines against methane-producing microbes. There is evidence that methane emissions have a heritable component, meaning we could breed cows that naturally emit less. How will selecting for lower methane affect other traits like productivity or feed intake? Will it meaningfully reduce absolute emissions or just emissions per unit of milk? These are known unknowns to be worked out through more data over successive cow generations.

It’s important for the industry to invest in these innovations (through R&D, trials, pilot programs) so we can convert more of these unknowns into “known knowns.” At the same time, we must recognise their current limitations and not become over-reliant on a silver bullet that might not materialise as hoped. 

Unknown Unknowns: Future innovations on the horizon

Finally, we acknowledge there are likely “unknown unknowns” in the quest to reduce dairy’s methane and carbon footprint – that is, solutions or game-changing ideas that haven’t even been conceived or proven yet. 

Scientists might discover entirely new ways to alter the microbial ecosystem of the cow’s rumen to produce far less methane, novel feeds or forages that inherently produce less methane during fermentation. It’s also possible that developments outside the cow, like carbon capture from barn exhaust, further shrinking the footprint of dairy farming. Being prepared to pilot and scale up the next discoveries are necessary.

However, it’s important to balance this future gaze with what we can do now. Unknown unknowns are exciting, but we cannot wait for unknown miracles. The climate challenge is here, and that’s why prioritising the “known known” strategies today is so important. 

Focus on what works, while exploring what might

In summary, cutting methane and carbon emissions from dairy cows will require both the application of proven practices and the exploration of new technologies. The “known knowns” are our low-hanging fruit, strategies like CattleEye which improve our ability to improve “known knowns” are ready to implement now, with well-documented benefits for productivity and emissions. 

At the same time, we must not ignore the “known unknowns.” Promising tools like methane inhibitors and dietary additives, as well as genetic selection for low emissions, deserve continued investment and trialling. 

By framing our approach around Rumsfeld’s trio; tackling the known knowns, investigating the known unknowns, and remaining alert to unknown unknowns, ensures we can make real progress today, while exploring innovations for greater gains tomorrow. 

Find out how CattleEye can help reduce your farm’s carbon footprint, contact us via contact@cattleeye.com