High metabolisable energy (HME) ryegrass

AgResearch scientists have been working over many years with the support of the government and commercial partners to develop the high metabolisable energy (HME) ryegrass to help improve livestock feed.

Background

High metabolisable energy (HME) ryegrass is a promising development providing an innovative solution that can significantly improve the quantity and quality of livestock feed. A genetically modified (GM) ryegrass with elevated leaf fat that provides an increase in energy content. This innovation has environmental, social and productivity gains.

A modified ryegrass that could reduce environmental impacts while boosting animal nutrition and farm productivity is expected to be fed to livestock for the first time next year to obtain an initial gauge of potential benefits.

AgResearch scientists have been working over many years with the support of the government and commercial partners Grasslanz Technology, PGG Wrightson Seeds and DairyNZ, to develop the HME ryegrass.

Scientist Luke Cooney discusses HME ryegrass.

Predicted benefits

Increase in available energy in ryegrass
Successfully increased oil content in ryegrass by 2.3%
Increased metabolizable energy (inc 1 Mj/kg DM – 10%)
Higher photosynthesis
Accelerated growth and increased biomass
Increased animal productivity
Improved water use efficiency
Reduced nitrated leaching and N2O (dec 6-7% urinary nitrogen)
Reduced methane emissions (10-15%)

It's the best science since Rutherford split the atom

Dr William Rolleston; South Canterbury farmer, biotechnologist, and former Federated Farmers national president.

How it works

The HME ryegrass works to create the high metabolisable energy, this is being done by adding and modifying two plant genes to increase lipid content in the leaf and enhance photosynthesis in the plant under some conditions.

The purpose is to increase the nutritional quality of ryegrass to drive greater productivity, but the research also suggests environmental benefits such as reduced nitrogen loss that can contribute to waterway contamination, and reduced emissions of greenhouse gases, methane and nitrous oxide. Current research suggests that methane reductions of 10 to 15 per cent may be achievable but the animal feeding trials are still to be undertaken to definitively test this.

For nitrous oxide, the opportunity is the improved animal nutrition leading directly to a reduction in urinary nitrogen excretion, resulting in reduced emissions and lower nitrate leaching; as well as the potential for reductions due to the HME plants influencing composition of the soil microbes leading to benefits in the nitrogen cycle.

Growing of HME Ryegrass and the required research has taken place indoors in contained conditions in New Zealand, according to regulations in place around genetically modified organisms. However, it has also been grown in regulated outdoor growing trials in the United States.

AgResearch's containment glasshouses at the Grasslands campus.

Into the future

Planning is now underway for a trial that is expected to start late next year, in which lambs will be fed both the HME ryegrass and a control ryegrass. To enable this, work is now underway to grow enough of the ryegrass in contained glasshouses in New Zealand that can be ensiled (preserved) for feeding to the lambs when the trial begins.

Scientists expect the trial to provide insights on methane emissions and urinary nitrogen excretion. Further confirmation in cattle will need to be performed in outdoor trials, most likely in Australia at a later date. The programme team earlier this year applied to Australia’s Office of the Gene Technology Regulator (OGTR) for permission to conduct growing trials in Australia.

Through the course of the application process with OGTR, it emerged that additional detailed analysis would be required on a specific issue for the application to proceed and be successful. The issue relates to an allergen (known as sesame oleosin) that may be present and could be released in the pollen of the ryegrass.

While AgResearch testing demonstrated that sesame oleosin is not expressed in the pollen of HME Ryegrass, a more rigorous test was required by OGTR. Given the timeframe and complexity associated with this more detailed test, the team reached the view that the best course was to withdraw the application to the OGTR and resubmit at a later stage.

The intention is to further reduce any future risk by replacing the sesame oleosin with an alternative that has no known allergenic properties.

The scientists are currently working on refining the composition of the ryegrass, based on a rice component rather than sesame, to support a further application for field trials and potential commercialisation of the ryegrass in Australia.

Results from the feeding trial commencing next year will guide next steps for the development of the HME Ryegrass programme and inform the potential for future commercialisation.