farting cow (methane)
farting cow (methane)

ScienceSeptember 18, 2019

Putting a cork in cow burps (and farts)

farting cow (methane)
farting cow (methane)

Covering Climate Now: Currently, more than a third of all of New Zealand’s greenhouse gas emissions come from sheep and cattle. There’s no easy solution, but a variety of anti-methane methods are being developed to curb this gaseous issue. 

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Join a cow or a sheep for dinner in the paddock and you might find yourself offended by their table manners. They belch. And fart. 

It’s not their fault, really – those burps and toots are made by tiny organisms living in their specialised stomachs (rumens) that feed on the waste from grass-fermenting microbes. 

But cows’ eating style is becoming a problem, not just for politeness’s sake. The methane belched out by ruminants (animals that ferment food in this way) is bad news for climate change. 

Methane doesn’t stick around in the atmosphere as long as carbon dioxide, but it’s much better at trapping energy in the atmosphere and heating Earth. More than a third of all of New Zealand’s greenhouse gas emissions come from gassy sheep and cattle. 

That’s why Kiwi scientists are ways to keep the cows but ditch the methane by feeding them differently, breeding low-gas animals, or developing drugs or vaccines. 

Some methods show real promise, touting the ability to drop methane emissions by a third. But whether they’ll actually make it to the field depends on figuring out some tricky science and getting farmers on board.

New Zealand’s unique situation

Other countries have turned to feeding cows seaweed or Soviet spacefood (algae) to cut down on the animals’ gassy emissions. That’s possible in the northern hemisphere because animals are often raised in barns where their feed comes from a bag. Farmers can more easily control what’s going in to change what’s coming out. 

New Zealand doesn’t have that option because, for the most part, Kiwi cows roam on pasture. “Ninety to 100% of the diet of our New Zealand ruminants is grass,” explains Mark Aspin, manager of the Pastoral Greenhouse Gas Research Consortium (a group of agriculture research organisations from around New Zealand). 

Grass-fed animals are something Kiwi farmers are proud of, and a major selling point overseas, he says, and we wouldn’t be in a hurry to give that up. 

Researchers have had only mild success at finding pastures that make animals burp less and work with New Zealand’s climate and farming style. For example, feeding animals on a pasture of almost entirely fodder beet could drop emissions by about a fifth, Aspin says, but then animals have trouble getting enough protein. 

According to the research consortium’s principal scientist Peter Janssen, “feed is not going to make a major contribution to reducing greenhouse gas emissions”.

Kiwi cows roam on pasture, so farmers can’t control what’s going in to change what’s coming out as easily as their northern hemisphere counterparts (Photo: Jill Ferry / Getty Images)

Breeding burp-less cows

If you can’t change what they’re eating, it might be worth changing the animals themselves. Consortium researchers have been breeding their own low-methane flocks of sheep for a decade. 

Right now they’re seeing methane burps drop by around 1.5% every time they breed them, or roughly every two years. Their current flock makes about 6% lower methane emissions than the average Kiwi sheep flock.

“It’s classic compound interest, genetics. You might make small changes but every season, every year you’re adding it up. It’ll add up to a reasonably important number over time,” says Aspin.

What’s different about these low-methane sheep is that they have smaller rumens and a different collection of microbes than their gassy counterparts. Smaller rumens mean feed flows through their systems faster, which means less waste as the feed ferments, and less for the methane-making microbes to feed on. The different microbe community also makes less waste, which works in much the same way.

A potential caveat is that these low-methane sheep have been selected purely based on how much gas they burp up. Breed genetics normally takes several factors, such as animal size or how many young they give birth to, into account. Sometimes improving one trait means another falls short.

At the end of the day, farmers get paid on how well their animal does in the milking shed or at the slaughter yard. “If you say [to farmers], ‘We can reduce your emissions but it’ll mean your animals won’t do very well’, that’s pretty much the end of the conversation,” says Aspin. 

So far their low-methane sheep are pretty similar to regular breeds in, for example, how much wool they grow or how much meat you get out of them. It’s unclear, though, whether that would change with future generations of selective breeding for low-methane.

Aspin says they’re in the process now of marketing their flock to selected sheep breeders across New Zealand. Up to 20 of them will pilot the new breed on farms next year and the hope is to roll out the low-methane breed after that. 

But sheep aren’t the biggest problem. Cattle belch out around two and a half times more methane in total compared to their woolly mates. Janssen and his team are looking at whether selecting for smaller stomachs and different microbes would work for cattle too, but he’s not sure they can get the same results. “Cattle are not just big sheep,” he points out.



Another plan is to get rid of the methane-making microbes (methanogens) altogether, while keeping those that ferment or digest the cow’s food. 

Scientists have already raised methanogen-less lambs that get on just fine with only the food-digesting microbes in their guts. The problem is these lambs were raised in a sterile lab where scientists could inject them with only the microorganisms they wanted. Not exactly practical in the paddock. 

If it’s not possible to raise animals without methanogens, it might be possible to stop them from working using drugs. 

The goal is to find molecules that create a kink in the chemical chain reactions that are crucial to the microbe’s survival. Inhibitors might, for example, block an enzyme that helps the microbe make energy. No energy and the microbe starves. 

Since methanogens are pretty similar regardless of whether you’re peering into a cow, sheep or deer stomach, the hope is that a few inhibitors could be used in a range of different animals.

The catch is these drugs can’t cause any side effects to the animals or to human consumers, and, ideally, not end up in the meat or milk at all. That means from a stockpile of millions of potential molecules, only about five or six classes of molecules make it to the testing phase. 

“It’s a bit of rollercoaster some days,” says Aspin. “You’re excited one day and disappointed the next.” 

The lengthy testing is necessary, says Janssen. “You have to be rigorous because the market will be rigorous.” 

Despite the long process, a few inhibitors are looking promising. In a lab trial, some curbed sheep methane emissions by a third

Researchers are now doing further on-farm tests to see if giving sheep these drugs has any negative side effects or if they show up in the meat. They’ll then figure out the best way to give animals the drugs, potentially via a capsule in their food. 

According to the consortium, farmers could see a range of inhibitor drugs on the market by 2023. 

The challenge with methanogen-inhibiting drugs is ensuring they don’t end up in the milk or meat (Photo by Martin Hunter/Getty Images)


One of the most promising, and creative, ideas Kiwi scientists are working on is a methane-busting vaccine. Farmers would give their animals (sheep, cattle or deer) a shot once and maybe follow up with a booster the following year. That would see their flock or herd’s methane levels drop by at least 20% for a lifetime. 

It’s a potentially low-work, high-reward solution. But it’s also the hardest to develop.

The goal is the same as for inhibitors: to knock out methanogens in the gut while leaving the rest of the digestive system intact. But instead of slipping cows a pill in their feed, vaccines use the animals’ own defence system against the gas-spewing nasties. 

Just like a vaccine for measles or polio gives the body a harmless version of the virus to trigger it to make antibodies that fight the real thing, methane vaccines give animals some part of the methanogen and get them to make antibodies against them. Those antibodies turn up in the saliva and get sent to the rumen when the cow swallows. 

“The animal is then naturally defending themselves against methanogens without humans needing to interfere all the time,” explains Janssen.

Success developing such a vaccine has been mixed. Prototype vaccines can trigger cows to make antibodies, and those antibodies can suppress methanogens in a lab, but they don’t seem to work when they get into a cow’s stomach. “The rumen is like pea soup. It’s really hard to figure out what’s going on in there and to find out what the limiting factor is,” says Janssen.

Figuring out what’s going on is a costly enterprise. The consortium alone invests $1.5 million every year into finding a vaccine that works. That investment is second only to funding inhibitor research, which gets around $2 million. To make it worthwhile financially, researchers need to show vaccines can lower emissions by at least 20%. 

Nonetheless, Aspin and Janssen are hopeful anti-methane shots will become a reality. There are other vaccines out there that target acid-making bacteria in the rumen, so the pair are confident they could do the same for these methane-making microbes too. 

“We haven’t seen yet a reason why it doesn’t work. We just have to figure out how to make it work,” assures Janssen. At this stage though, according to Aspin, “the vaccine still eludes us”.

Assault from all angles

Despite the scientific struggles and high costs, the agriculture industry is under pressure from the public and government to find ways to reduce their emissions. The question is less which options are available and more which options can be proven effective and developed fast enough to meet 2030 and 2050 emissions targets.

Most likely farmers will use a suite of anti-methane methods in the future. “One size doesn’t necessarily fit all,” says Janssen. “For different farming systems some [techniques] may be better or more applicable than others.”

Having the options available is one thing, but whether farmers will choose to breed their ewes with a less-burpy ram or go through the effort of vaccinating all 400 or so of their cows remains to be seen. Federated Farmers have cried out to lower emissions targets or provide the ability to plant trees to offset methane instead. However, with farmers facing the prospect of soon having to pay for their emissions, a less gassy flock or herd might be appealing economically. 

“We do have to do our bit, and I think all humans have to do their bit,” says Aspin. “We’re trying to drive forward as quickly and effectively as we can.”

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