Scientists bust belching bug

Scientists have pinned down one of New Zealand's worst polluters - the bug that makes cows belch methane.

They've mapped the genome of a gas-producing microbe in the stomachs of cattle, sheep and deer and will use the information to reduce the environmentally damaging emissions.

"It's a bit like having a parts list for the organism," said Pastoral Greenhouse Gas Research Consortium manager Mark Aspin. "Having the genome sequence allows you to be very specific about what you're trying to shoot for."

Methane and nitrous oxide from farming account for almost half the country's emissions. The targeted microbe is the biggest offender among hundreds that produce methane from hydrogen and carbon dioxide in the stomachs of ruminant animals.

"It's early to tell how much we can reduce it but we'd be optimistic," Aspin said. Diet supplements overseas have been shown to reduce methane by 10 to 20 per cent. "But we haven't been able to replicate that in a cost-effective way."