Agricultural scientists who have spent years looking at how to create pasture plants which could reduce the methane emissions from livestock say it may be possible to produce a clover that will do the job.

Scientists from AgResearch and one of its subsidiaries, Grasslanz Technology Ltd, said today they can produce an improved cultivar of white clover to give cows and sheep extra protein and at the same time reduce emissions of methane and nitrogen waste, while improving animal health.

Nearly half of the nation's greenhouse gas emissions are generated by agriculture, but farmers have resisted taking accountability for their share of emissions on the grounds that they do not have an economic way to combat the methane emissions.

AgResearch scientists Garry Waghorn and Michael Tavendale have previously shown that condensed tannins found in some pasture species, such as lotus, a legume, can directly reduce methane emissions by as much as 16 per cent, and Dr Tavendale has predicted that pastures containing condensed tannins are likely to become increasingly important to farmers.

Condensed tannins are chemical compounds that can bind to and protect protein being broken down in the stomachs of sheep and cattle, but legumes such as lotus are difficult to establish and do not keep growing in grazed pastures.

Now the scientists are working on a white clover that contains concentrations of the condensed tannins -- normally only found as trace amounts in white clover and are entirely absent in grasses.

The researchers found AgResearch two types of clover which do have condensed tannins in their leaves, and compared their genetic make-up to find a gene that can increase the levels. A related gene was found "switched off" in white clover and the scientists are now looking at how the gene can be re-activated to create a white clover which has not been genetically engineered, but will have the sought-after tannins.

AgResearch science general manager Jimmy Suttie said that such a cultivar could benefit not only farmers but the environment: "Currently white clover contains extremely low levels of tannins found only in the flowers, and if we can alter this to allow condensed tannins to accumulate to effective levels in leaves then we'll have a major benefit.

"There is evidence that tannins can reduce methane emissions from ruminants, and this increases the importance of our work," said Dr Suttie.

A clover which reduced gas retention in livestock could also reduce bloat sometimes seen in animals eating clover-rich pastures when pasture growth is rapid in spring.