“First step” discovery in NZ efforts to reduce livestock methane emissions

A team of AgResearch scientists is reported to have identified five compounds that reduce methane emissions from livestock by up to 90 percent in initial short-term trials.

The announcement was made this week at the Agricultural Greenhouse Gas Mitigation conference in Palmerston North.

Methane, a potent greenhouse gas, accounts for 44 per cent of New Zealand’s total emissions. Most of this methane comes from livestock.

A report from Radio NZ quoted AgResearch principal scientist Peter Janssen, who co-ordinates the methane research programme.

He said the findings were the culmination of five years work, during which the team screened more than 100,000 compounds through computer-based searches and in laboratory experiments.

The screening process identified five compounds that have now been tested successfully in sheep, showing a significant reduction in methane production over a two-day period.

“The programme has been looking for new types of inhibitors of methane production from the rumen. This can be regarded as a first step in the process towards developing something that can be used on the farm.”

Because methane accounts for most of New Zealand’s agricultural emissions, the Government and pastoral industry formed a partnership to fund research to develop inhibitors that would specifically knock out methanogens but leave the rest of the rumen microbial community intact.

Janssen told Radio NZ the effort was now paying off.

“These initial steps are relatively short-term trials in sheep and they show that you get a reduction of methane between 30 to 90 per cent. It’s a very exciting result but there’s still a lot of checking to be done before you actually get something that a farmer can use safely.”

AgResearch scientist Ron Ronimus, who leads the methane inhibitor discovery project, said the team made use of genetic information that became available when the first complete genome of a methanogen was published in 2010.

Of the roughly 500 known genes, the team focused on finding compounds that would inhibit the function of those that are known to be involved in the production of methane.

Methanogens belong to a group of ancient microbes known as archaea, and that offered an advantage for the team.

“They are very different from other bacteria, protozoa and fungi that are also in the rumen, breaking down the fibre during the fermentation.”

The team scaled up the discovery process by screening thousands of potential compounds in the laboratory and then testing the most promising inhibitors in sealed containers of real rumen fluid.

“It’s a very thick funnel if you like, we’re putting many compounds in at the top and getting very few out at the bottom,” he said.

Each of the five compounds had to pass toxicity tests before they could be tested in sheep in respiration chambers that allow the science team to monitor changes in methane emissions precisely, as well as feed intake.

“The intention is to only hit the methanogens,” said Peter Janssen. “The nice thing about the way the programme is structured is that the last major test before the compounds go into the animal is to test them in rumen contents that have been taken from an animal.

“If it has a general impact on other microbes in the system, then you see that the whole fermentation shuts down. If it’s only affecting the methanogens then you see that the fermentation continues just like normal, and it’s only the methane part that is affected. If it then passes subsequent toxicity testing then we know we can safely try it in an animal.”

Ron Ronimus said the goals now were to test if the inhibition effect lasts long-term and whether it can be used to increase animal productivity.

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