Dulse (or seaweed for the uninitiated) has long been a delicacy enjoyed in Ireland. The tradition can be traced back more than 1,400 years to the writings of St. Columba, but climate change research about to begin on the island could soon see our cows enjoy the salty snack too.

Northern Ireland’s first farm trials testing the potential of seaweed to reduce emissions in dairy herds are set to begin in October, Agriland can reveal.

The study will examine the effect of feeding cows seaweed on rumen fermentation and whether its inclusion can suppress methane emissions as a byproduct.

It might seem peculiar, but the concept is quickly gaining steam among top researchers, with a project investigating the effects of feeding seaweed to sheep also set to begin in the Republic next month.

The two trials form part of the €2 million Seasolution project led by Teagasc and carried out in collaboration with Queen’s University Belfast (QUB), the Agri-Food and Biosciences Institute (AFBI), the Institute of Technology Sligo, as well as institutions in Norway, Sweden, Germany and Canada.

Each of the institutions involved will run their own trials as part of the project, with experiments in Germany and Sweden also set to start later this year.

Northern Ireland seaweed trials

The Northern Ireland trials will be led by Queen’s University and take place at AFBI Hillsborough. The study will focus on dairy cattle and will seek to establish the optimum volume of seaweed to include in a grass silage based ration, while also measuring seaweed’s effect on feed intake, milk production and composition, nutrient digestibility, and nitrogen utilisation.

If successful, it’s hoped the findings could be applied locally on farms contributing to the sustainability of the agri-food industry.

In a separate project, Queen’s and AFBI will also take the trials further, looking into how feeding seaweed could benefit beef production. However, it could be a while before anyone enjoys seaweed-fed steaks; the beef aspect of the study will likely start two years later and will also measure the effect on growth rates, as well as any changes to meat quality and composition.

Researchers will also seek to screen different seaweed species for their methane-reducing potential to establish if some native varieties have more potential than others.

It comes on the back of a lab-based study which finished last year at Queen’s, confirming that the inclusion of seaweed in livestock diets had the potential to suppress methane emissions from the rumen.

Sharon Huws, animal scientist and microbiologist at Queen’s University Belfast, who is overseeing the Northern Ireland aspect alongside AFBI researcher Tianhai Yan, said the research had the potential to “revolutionise the future of agriculture”.

“This is a very exciting space,” she said.

“It could be the silver bullet we have been trying to find in the move towards carbon-neutrality.”

Irish sheep trial

Meanwhile, south of the border, a project led by Teagasc investigating the effect on sheep, particularly lamb production, will begin in May at a research farm in Athenry, Co. Galway.

Dr. Maria Hayes, senior scientific research officer at Teagasc Food Research Centre, explained seaweeds contain bromoform, which has been linked to negative effects such as damage to the ozone layer.

However, red seaweed (Asparagopsis), the kind which has been used in previous livestock emission studies, contains much more than others. Researchers hope that locally-grown alternatives containing less bromoform may have fewer unintended effects.

Dr. Hayes said: “We have been working on identifying the ‘best’ seaweeds and seaweed extracts to bring forward to animal trials in sheep, cattle and dairy cows.

“To be considered for trial, the seaweeds and seaweed extracts must be available in Europe in quantities that will permit their use as animal feed or feed additives. They must be affordable and they must be able to reduce methane emissions without negative effects on health and nutrition in the animal or in humans.

“Our focus is on native, abundant seaweeds containing actives like tannins, carbohydrates, peptides – actives other than bromoform. We use seaweeds like Asparagopsis aramata and A. taxiformis as positive controls only.

“The methane mitigation effect of Asparagopsis sp. is well documented by other research groups, but there are concerns about the availability of these seaweeds, the effects of high levels of bromoform (which is the active in Asparagopsis sp. that causes methane reduction) on the ozone layer, and potential negative health effects.

“The project has partners from Ireland and Northern Ireland, Germany, Sweden, Norway and Canada, and will generate concrete data on the benefits of seaweed use as an animal feed or feed additive to reduce methane. Initial animal trials in sheep will begin in May 2021,” she said.

Why cow burps matter?

Methane emissions are a major challenge for the industry locally, particularly as government focus moves towards net-zero goals.

Methane accounts for 23% of Northern Ireland greenhouse gas (GHG) emissions, with 80% of that originating from agriculture.

While there is much debate over how methane should be measured, and whether it should be measured in terms of its CO2 equivalence due to its shorter lifespan, it remains the industry’s largest pollutant.

Most of that comes in the form of cow burps; according to the Department of Agriculture, Environment and Rural Affairs (DAERA) Greenhouse Gas Inventory, enteric fermentation (digestion in the rumen) remains NI agriculture’s largest source of GHG emissions, generating more CO2 equivalent gases than fertiliser use, manure management and agri-combustion combined.

It’s a similar situation in the Republic of Ireland, where methane accounts for almost a fifth of national emissions and 58% of Irish agricultural emissions.

Seaweed studies

There have been some big claims in recent years about the potential of seaweed as a solution. One 2016 Australian study claimed including seaweed at just 0.2% of Dry Matter Intake (DMI) reduced methane emissions by up to 98% in Brahman-Angus cross steers.

Last year, a small-scale experiment carried out in Sligo by seaweed start-up Dúlabio also found significant potential for red seaweed as part of a grass-based diet for beef cattle. It claimed that including seaweed in the diet reduced the number of ‘methane eruptions’ (or burps) by 79.5% but notably, the study did not measure the effect on the overall volume of emissions. The study has not been published in any journals.

However, the verdict is certainly not clear. A trial carried out by Teagasc last year on pasture-grazing cows, found including seaweed in their feed had no effect in reducing emissions. It did, however, find that including phytochemicals, the active ingredient from seaweeds, caused a slight increase in milk solids but did not reduce methane emissions per kilogram of solids.

Teagasc researcher Dr. Ben Lahart explained the disparity in results may partly come down to the type of seaweed used.

“It could be due to a number of reasons,” he said. “The indoor experiments are using predominately red sea, within our study we used a very small proportion of that within the supplement.

“The majority of the seaweeds were just green and brown seaweeds, which have been previously shown to be not as effective in mitigating methane. Research also shows the effect of red seaweed diminishes the longer it’s been in storage. Our supplement would have been waiting a number of months before it was fed out to the cows, so it could have lost its efficacy in that storage period.

“Then you have to add in the fact that [the trial involved] grazing while the others have been indoors – and in that indoor study they were continuously offered the supplement throughout the day, whereas we were offering it twice daily – so there are a number of different factors.”

It raises important questions over the best way to proceed. If the crop’s freshness is central to its efficacy, importing seaweed is likely to be ineffective, making researchers efforts to find an effective locally-grown variety critical to the concept’s success in Ireland.

One alternative suggestion has been that a synthetic additive could be derived from the most-suited seaweeds. However, it’s much more challenging for synthetic compounds to gain Food and Drug Administration (FDA) approval as feed additives, often taking several years to complete the process.

A rock with a good crop of dulse was once said to be worth three cows in Ireland, but with the industry now facing swingeing livestock reductions, the solution to the methane problem could be worth far more.

Editor’s note: This is an updated version of this story.