Could Australian seaweed reduce methane from cows?

The effort, spurred from a study in 2014, comes hot on the tails of other antipodean-led breakthroughs in understanding a cow’s methane production.

The seaweed, Asparagopsis ​taxiformis​, grows prolifically off the Queensland coast. It was the only species found to have a fart-free effect on cattle in a comparative study five years ago led by Csiro, Australia’s government research agency.

The research found the metabolites in the seaweed disrupt the enzymes that were found last month to be responsible for the production of methane.

Nick Paul, a USC associate professor and leader of its seaweed research group, believes Australia could cut its greenhouse gas emissions by 10% if it were to grow enough of the seaweed for every cow in the country.

Cows and other ruminants contribute 37% of the methane emissions resulting from human activity. A single cow on average produces between 70 and 120 kg of methane per year. There are about 1.5 billion cattle worldwide.

“Seaweed is something that cows are known to eat. They will actually wander down to the beach and have a bit of a nibble​,” Dr Paul said.

“When added to cow feed at less than two percent of the dry matter, this particular seaweed completely knocks out methane production. It contains chemicals that reduce the microbes in the cows’ stomachs that cause them to burp when they eat grass​.”

Before the USC team can commercialize the seaweed, and effectively create a new industry, they must first find the perfect growing conditions to move crops from the laboratory to large outdoor aquaculture tanks.

To this end they have been working at the Bribie Island Research Centre in Moreton Bay to learn more about growing the seaweed species, with the goal of informing a scale-up of production that could supplement cow feed on a national or even global scale.

“This seaweed has caused a lot of global interest and people around the world are working to make sure the cows are healthy, the beef and the milk are good quality​,” Dr Paul said.

“That’s all happening right now. But the one missing step, the big thing that is going to make sure this works at a global scale, is to make sure we can produce the seaweed sustainably​.”

To this end, they are also looking at how to ramp up the concentration of the A. taxiformis​ metabolites so less seaweed is needed for a similar digestive effect.

The source of a cow’s methane production only recently became apparent, after a New Zealand government-funded team identified a group of stomach-dwelling microbes that produce the gas when digesting feed.

Collaborating with researchers across the Tasman, and teams from the US and Japan, the Kiwis found the culprit.

Methane emissions from animals account for around a third of New Zealand’s emissions. The cow itself does not produce methane but rather a group of microbes, called methanogens, which live in the rumen and produce methane mainly from hydrogen and carbon dioxide produced as the feed breaks down there.

The rumen is the first stomach in the digestive system of ruminant animals.

The study, published in July, was the first to identify the main rumen microbes and enzymes that both produce and consume that hydrogen.

The findings are important because scientists can now target the supply of hydrogen to methanogens as a new way of reducing animal methane emissions.

Work will move to focus on screening specific compounds that can reduce the supply of hydrogen to the methane producers without compromising animal performance.

Research will also seek to find ways to divert hydrogen away from methanogens towards other rumen microbes that do not make methane.

“It opens up a new approach to reducing livestock methane emissions. This is vital for New Zealand to meets its greenhouse gas emission targets and to ensure the farming of ruminants is sustainable into the future​,” said program leader Graeme Attwood, principal scientist at AgResearch, New Zealand’s Csiro counterpart.

Shortly afterwards in July, in Adelaide, more scientists had concluded a study that had looked at breeding in a bid to reduce the methane emissions of cattle.

Their study showed that the genetics of an individual cow strongly influenced the make-up of the microorganisms in its rumen—the first stomach in the digestive system of ruminant animals.

“What we showed is that the level and type of methane-producing microbes in the cow is to a large extent controlled by the cow’s genetic makeup​,” said one of the project’s leaders, John Williams, a professor in the University of Adelaide’s School of Animal and Veterinary Sciences.

“That means we could select for cattle which are less likely to have high levels of methane-producing bacteria in their rumen​.”

The research comes out of a project called RuminOmics, led by the Rowett Institute at the University of Aberdeen in Scotland and involving academies in Europe, Israel and the US.

The researchers analyzed the microbiomes from the ruminal fluid samples of 1,000 cows, along with measuring the cows’ feed intake, milk production, methane production and other biochemical characteristics.

Although this study was carried out on dairy cows, the heritability of the types of microbes in the rumen should also apply to beef cattle.

“Previously we knew it was possible to reduce methane emissions by changing the diet​,” said Dr Williams.

“But changing the genetics is much more significant. In this way we can select for cows that permanently produce less methane​.”

Professor Williams believes breeding for low-methane cattle will, however, depend on selection priorities and how much it compromises selection for other desired characteristics, such as meat quality, milk production or disease resistance.

“We now know it’s possible to select for low methane production​. But it depends on what else we are selecting for, and the weighting that is placed on methane. That’s something that will be determined by industry or society pressures​.”

The researchers also found a correlation, although not as high, between the cows’ microbiomes and the efficiency of milk production.

“We don’t yet know, but if it turned out that low-methane production equated to greater efficiencies of production—which could turn out to be true given that energy is required to produce the methane—then that would be a win-win situation​,” Dr Williams added.