Could genetics hold key to low methane sheep?

Do environmentalists dream of low-methane sheep?

If so, they may be cheered by research currently under way in New Zealand that indicates some of sheep naturally emit less methane than others, meaning that selective breeding could one day be used to create less gaseous sheep.

A low-methane flock produced about 20 per cent less than a high-emitting one when both were fed the same grass, according to a government-backed study by the Pastoral Greenhouse Gas Research Consortium.

Similarly, when fed silage and other dry food, the less gaseous sheep produced eight per cent less methane than their flatulent cousins.

In fact, no matter what they ate, the low-methane sheep consistently produced less emissions, which the scientists believe could be attributed to genetics.

"For the first time we have opened up the possibility we could breed animals with lower greenhouse gas emissions," Harry Clark, the scientist leading the study, told the New Zealand Herald newspaper at the weekend.

Clark, a researcher at state agricultural research institute AgResearch, said that New Zealand was fast emerging as a world expert in tackling emissions from livestock. "We definitely lead the world in this," he added.

The research body is one of the study's backers, along with the government's Foundation for Research Science and Technology, industry bodies Meat & Wool New Zealand, DairyNZ, Fert Research and DEEResearch, and agribusinesses Fonterra and PGG Wrightson.

Scientists tested individual sheep for their methane output by putting them into a sealed breathing chamber that measured the amount of gases they released after being fed a variety of foods.

Consistently low-emitting sheep were added to one flock, while their high-output counterparts were put into a second flock. The emissions of both flocks were measured and compared.

Further tests will be used to determine whether less gaseous sheep are capable of producing milk, wool and meat of equal or greater quality and quantity than other sheep, and if they passed on their low-gas genes to offspring.

It is hoped that the study will eventually lead to the breeding of low-methane sheep, cows, goats and deer. The research consortium aims to reduce greenhouse gases per unit of milk, meat or wool by 10 per cent on 2004 levels by 2013.

Greenhouse gas emissions from agriculture are a serious matter in New Zealand, where nitrous oxide and methane produced by livestock account for about half the nation's greenhouse gases.

In 2003, New Zealand legislators proposed a "fart tax" that would have put a levy on livestock emissions. After it failed to pass into law, the Pastoral Greenhouse Gas Research Consortium was created as an alternative means of addressing agricultural greenhouse gas output.