Reducing animal methane emissions feasible

The "Global Rumen Census" project analysed the microbes responsible for methane emissions from a wide range of ruminant animals around the world.

Collaborating with 140 researchers from 73 institutions, the New Zealand-led project found similar bacteria and methanogens dominate in nearly all rumens across a wide variety of species and animal diets.

This means that new technologies that seek to reduce methane emissions by influencing rumen microbes should have global applications.

The results of the Global Rumen Census have been released on 9 October 2015 in the open-access journal Scientific Reports.

The international collaborators worked alongside six main AgResearch authors, led by Gemma Henderson and Peter Janssen of AgResearch Grasslands, Palmerston North.

"It was an honour to be involved with such a successful international collaboration," says Henderson.

She has been working at AgResearch for eight years on projects related to methane mitigation and the Global Rumen Census project.

"One of the most exciting things for me was the enthusiasm generated internationally with so many people being interested in what we were doing and wanting to contribute. That was very rewarding."

Samples for the census were collected over two years.

"We initially thought it would attract about 200 samples but the international interest was immediate and quite large. The sample pool grew to over 900 and we selected 742 of those samples to include in the project." she says.

Samples came from places as far as the Slovenian mountains and remote islands off the Chilean coast. As well as the expected samples from sheep, cattle, deer and goats, there were also some from buffalo and giraffes.

The rumen is the modified foregut of these animals. Feed is fermented by the microbes in the rumen, allowing the animal to extract energy from feed such as grasses that otherwise could not be digested. These microbes are therefore essential for ruminant productivity.

Unfortunately, one of the by-products of this fermentation is the greenhouse gas, methane, produced by microbes called methanogens.

"The rumen methanogens turned out to be highly similar species in all rumens across the world. So, only a few species appear to be responsible for all the methane produced by ruminants everywhere, which means mitigation strategies can be developed to target the few dominant methanogens," says Janssen.

Janssen says the rumen microbes ended up being more similar than they had expected. Mostly they were the same in all samples, but some microbes were more strongly associated with certain hosts and some with certain diets.

"Even more interesting from a New Zealand perspective, was the finding that the methane producing microbes, the methanogens, are the same everywhere."

Harry Clark, director of the New Zealand Agricultural Greenhouse Gas Research Centre and co-chair of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases, says this study shows the real power of international research collaboration.

"This study has provided knowledge that no country could have delivered on its own, and the benefits are also global." says Clark.

"The Global Rumen Census shows that new mitigation technologies that tackle the microbes responsible for methane production in ruminants can make a real difference at the global scale. Modifying the rumen is an enormous challenge, but collectively we have a chance to get there."