Scientists seek global warming clues in sheep's belches

By SIMON COLLINS

Sheep are playing their part in a bid to cut New Zealand's contribution to global warming by more than 10 per cent.

AgResearch scientists have fitted the sheep with devices to measure the amount of methane they let out when they belch.

Methane released by New Zealand's 45 million sheep and 8 million cattle accounts for 44 per cent of locally produced greenhouse gases, which trap heat in the atmosphere.

Dr Keith Joblin, who leads a four-person team studying the problem, believes it should be possible to reduce the amount of methane from animals by 30 per cent - cutting the country's global warming effect by more than a tenth.

"There are huge implications and opportunities for New Zealand," he says.

Any technology developed here could also be applied to grass-fed animals in Latin America, South Africa and elsewhere.

The problem is particularly bad in New Zealand because the microbes that digest the grass in livestock here have a much tougher job than those in grain-fed animals in Europe, North America and Japan.

"Because grass is more difficult to digest, more methane is produced."

The problem occurs to some extent in all ruminant species - animals that "chew the cud", or return partly digested food from their first stomachs to their mouths for further chewing.

Ruminants also include deer, goats and giraffes.

"They belch it out, they don't fart it," Dr Joblin says. "Ninety per cent comes out the front, not the back."

The New Zealand scientists are collaborating with a French group that has successfully reared sheep on special diets that do not produce methane.

Measuring devices fitted on AgResearch's flock near Palmerston North have also found huge natural variations in methane belching.

"We were surprised to find that similar animals sometimes produced very different amounts of methane," says Dr Joblin.

"Maybe 10 per cent produced a lot less than the others.

"So there is something naturally going on that, if we can understand and exploit it, could provide good targets for us to lower the methane."

The clues lie in the various microbes in the sheep.

"One small group of them digest the grass and produce hydrogen. The methane-producing microbes feed on this hydrogen to make methane ...

"A scientist from France has brought to us microbes which do remove hydrogen but don't produce methane.

"They produce acetate - nutrients which the animal absorbs."

Dr Joblin says the research programme aims to find a natural process that will change the mix of microbes in the animals.

nzherald.co.nz/climate

Intergovernmental Panel on Climate Change (IPCC)

United Nations Environment Program

World Meteorological Organisation

Framework Convention on Climate Change

Executive summary: Climate change impacts on NZ

IPCC Summary: Climate Change 2001