Methane Emissions From Grazing Cows: 5 Proven Ways Teagasc Research Can Cut Them

Methane emissions from grazing dairy cows may be lower than national inventories assume, according to a new review featuring research from Teagasc, Ireland's agriculture and food development authority. In an article published on 8 November, Dr Ben Lahart, Research Officer at Moorepark, and Dr Muireann Egan of the Teagasc Climate Centre summarise what drives methane in pasture-based dairy systems and which mitigation options work best.

Why Methane Emissions Matter for Dairy

Ireland has committed to cutting greenhouse gas emissions by 51% by 2030, with agriculture targeted to reduce its emissions by 25% compared to 2018. According to provisional 2025 estimates from Ireland's Environmental Protection Agency, agriculture accounted for about 39% of national greenhouse gas emissions. Methane is the second-largest contributor after carbon dioxide, making up 28.8% of total national emissions.

In pasture-based dairy systems, enteric methane is the dominant greenhouse gas. It is produced when microbes in the rumen break down feed, and is released mainly through belching.

Baseline Emissions May Be Overstated

Large-scale methane measurement on farms is difficult, so national inventories rely on prediction models that express methane as a fixed share of gross energy intake. Better measurement technology is changing that picture. Studies by Teagasc, Wageningen University and DairyNZ have found that baseline methane emissions from lactating cows grazing pasture are lower than inventory models currently assume. This should lead to more accurate estimates and better-informed mitigation decisions.

1. Feed Additives

Additives such as Asparagopsis seaweed and 3-NOP have cut methane emissions by 20–40% in housed systems fed total mixed rations. In grazing systems, however, their effect is weaker because cows receive them only twice a day at milking. Alternative delivery methods are being tested, but uncertainty over how much additive each animal actually eats makes results inconsistent and complicates regulatory compliance.

2. Vaccines

Vaccines that target methane-producing microbes are under development, but more work is needed to prove they work in field conditions.

3. Breeding

Genetic selection offers permanent and cumulative gains. Research shows that cows with high genetic merit on Ireland's Economic Breeding Index produce more milk solids without producing more methane, lowering methane per unit of output. Direct selection for a methane trait could deliver annual reductions of 0.5–1%, though this must be balanced against productivity, efficiency and profitability.

4. Better Grass, Less Silage

Grazing management plays a major role in reducing methane emissions. Research from Teagasc and Wageningen University shows that high-quality spring grass leads to larger methane reductions than summer and autumn grass. Turning cows out to grass earlier in spring and reducing silage feeding both help. During the main grazing season, keeping swards highly digestible, with pre-grazing covers of around 1,400 kg dry matter per hectare, lowers methane per unit of milk solids and reduces the need for concentrates, which carry their own off-farm emissions.

5. Smarter Sward Mixes

Results from alternative sward species are mixed. Adding white clover to ryegrass has sometimes increased total methane output, although clover's main benefit is replacing synthetic nitrogen fertiliser and the nitrous oxide linked to it. More recently, multi-species swards of grass, clover, plantain and chicory have shown potential to reduce methane emissions relative to milk solids produced.

Relevance for India

India's dairy system is very different, built on smallholders, crop residues and mixed feeding rather than intensive grazing. Still, the principles carry over: higher-quality, more digestible feed and better genetics reduce methane emissions per litre of milk. Indian initiatives on ration balancing, improved fodder and biogas from dung reflect similar thinking, as seen in our report on Delhi's 200-tonne biogas plant. European processors are also linking farm payments to emission cuts, as in Arla's farmer incentives.

The key takeaway: Methane emissions from grazing dairy cows may be lower than inventories suggest, but cutting them further will rely on better grass management and breeding, as feed additives remain hard to deliver at pasture.

Read the full article from Teagasc.

Source: Teagasc | DairyNews7x7