US testing begins on genetically modified ryegrass developed in NZ

Genetically modified ryegrass developed to reduce methane emissions and nitrate discharges by livestock is being tested in the United States.

Limits on GM experimentation in New Zealand have resulted in several ryegrass varieties developed by scientists from AgResearch being sent offshore for further testing.

Scientists hope the US trials will verify the results of lab work and modelling carried out here which found the grasses could reduce methane emissions, cut pasture costs and increase production on New Zealand dairy farms.


The five-year field and animal nutrition trial programme is a joint project with DairyNZ and will test up to four high metabolisable energy ryegrass lines. The last two years will include animal nutrition and greenhouse gas emissions testing on animals in containment.

Speaking at DairyNZ's Farmers' Forum in Stratford, AgResearch senior scientist Kim Richardson said the forages contained a GM technology that improved photosynthesis by as much as 20 per cent, leading to 50 per cent higher plant growth rates.

"These plants also contain higher levels of lipids in the leaf - about seven per cent where a non-GM variety has about 3.5 per cent," Richardson said.

"That increases metabolisable energy by about 10 per cent and improves the overall nutritional value of the plant."

Lipid content in ryegrass was more seasonal than in GM varieties and two genes had been modified to make the lipids stable in the leaf, he said.

"Initially we modified one gene to boost lipids and it worked but within three or four weeks it was back down. Modifying another gene meant we were able to stabilise lipid levels."

For every 1 per cent increase in lipids, a 5 per cent decrease in methane could be expected, meaning an overall reduction of up to 23 per cent, Richardson said.

"GM crop trials in New Zealand are limited to the greenhouse and these results will have to be verified by animal field trials but that's what we're hoping to achieve though the US programme."

Although there were many arguments both for and against the use of GM crops, natural variation in lipid levels did not exist in ryegrass germplasm and stabilising lipid content was not going to happen naturally, Richardson said.

Modelling and lab work already carried out in New Zealand showed several other potential benefits of the GM ryegrass in dairy grazing systems, including a reduction in the total urinary nitrogen load of 6 to 7 per cent, resulting in reduced nitrate leaching and nitrous oxide emissions.

The plants had also shown a 9 per cent increase in water use efficiency, which should improve drought resistance, Richardson said.

"HME ryegrasses have a better root system, improved water use efficiency and drought tolerance so it could be a more reliable feed supply for farmers on non-irrigated or drought-prone land," he said.

The higher growth rates, hardiness and improved nutritional value of GM ryegrasses could boost farm revenues by as much as $900 per hectare, Richardson said.

A recent grant from the Ministry of Business, Innovation and Employment's Endeavour Fund, along with funding from AgResearch, DairyNZ and other stakeholders, meant an investment of $25 million over five years into the genetically modified forages research.