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Methane-reducing feed additives and their effect on milk

Why is this research important?

Dairy is central to Ireland’s economy, producing world-class milk and milk products from pasture. But the sector also faces the challenge of reducing greenhouse gas emissions, with methane from cows making up 63% of agricultural emissions. Methane is especially potent, trapping up to 87 times more heat than carbon dioxide over 20 years. The positive side is that methane only lasts about 12 years in the atmosphere, making it one of the fastest levers to slow climate change if reduced at source.

One promising option is feed additives that act in the rumen, where methane is produced during digestion. Additives such as red seaweed (Asparagopsis taxiformis), 3-NOP, calcium peroxide, and certain oils have shown strong results in indoor feeding systems. However, applying them in Ireland’s pasture-based systems is more challenging, as grazing cows don’t receive consistent doses year-round.

This four-year PhD project is investigating which solutions can work in real Irish conditions, while also checking how they affect milk and dairy quality. Protecting Ireland’s “grass-fed” reputation in premium markets is vital, so understanding any impacts on milk composition and processability is as important as reducing emissions.

What the research tells us?

Over the past two years, our team has conducted a series of trials to evaluate the effectiveness of methane-reducing feed additives in Ireland’s pasture-based dairy systems. These trials focused on three promising additives: 3-nitrooxypropanol (3-NOP), Asparagopsis taxiformis (red seaweed), and calcium peroxide. Each was assessed not only for its ability to reduce methane emissions, but also for its impact on milk quality and butter characteristics. Methanogenesis suppression mechanisms cause shifts in fermentation pathways that produce volatile fatty acids in the rumen. Accompanying this shift is a net gain in energy which would have been used in the methanogenesis process.  In addition, we noted subtle changes in the fatty acid profiles of raw milk and butter. These nuances could impact on milk flavour and processibility into key consumer-focused commodities.

Milk quality and composition

Overall, no negative effects on milk quality were found in any of the trials. With calcium peroxide, the milk performed as normal, though some small changes in the fat profile could make butter a little firmer or change how easily it spreads.

In the case of 3-NOP, we saw minor increases in certain proteins and fats. These may slightly influence how the milk behaves during processing, and in rare cases, could make it test closer to goat’s milk.

For Asparagopsis (red seaweed), the milk quality and processing properties were mostly unaffected. However, there were some small changes in the protein balance, which could have knock-on effects for products like cheese, yoghurt, or infant formula.

In short, the differences were subtle, but they underline why it is important to look not just at methane reduction, but also at how additives may influence the quality and processability of milk for the premium products Ireland is known for.

Butter Properties

When cows were fed 3-NOP, the butter was consistently softer than normal. It melted more easily and was less firm, but its colour and overall appearance stayed the same.

With Asparagopsis (red seaweed), butter also softened depending on the amount fed. Higher doses led to a more noticeable softening compared with lower doses or the control group. Again, the colour remained unchanged.

Overall, the main effect seen in both additives was softer butter, which in many cases could be a desirable trait for consumers, especially for spreadability.

Conclusion

Delivering consistent doses in grazing systems can be challenging, but feed additives like calcium peroxide, 3-NOP, and Asparagopsis (red seaweed) show strong potential for reducing methane emissions. Crucially, no negative effects on overall milk quality were observed.

The most noticeable change was softer butter, which may even be a benefit for consumers.

Our ongoing work is looking closely at how these feeds influence the cow’s rumen microbes, as well as carrying out sensory testing. This ensures that new additives not only cut emissions, but also protect cow health, milk quality, and the products made from it, supporting both farmers and the wider dairy industry.

Key outputs

The findings from this research have been presented at Teagasc Climate Centre Methane Pillar workshops, Food Chemistry and Technology seminars, industry stakeholder events, and to butter manufacturers. Manuscripts on calcium peroxide, 3-NOP, and Asparagopsis, which will provide comprehensive details of each result and changes in milk composition and functionality, are currently in preparation for peer-reviewed journals.

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