Pasture Biotechnology update #3

These technologies can be used to change the DNA of a living organism, such as a plant or animal, through either inserting, replacing, or deleting genetic material.

Opportunities from these technologies include greater farm productivity, better animal health and improved environmental results that may include reduced greenhouse gas emissions and less nitrogen loss that has the potential to contaminate waterways.

Work is underway to understand the potential benefits of these technologies and to ensure that those benefits outweigh any potential risks. In this newsletter, we provide the third in a series of updates on the progress of three pasture programmes that are currently underway; either indoors in containment in New Zealand or in field trials offshore.

High Metabolisable Energy (HME) ryegrass

The first livestock feeding trial with AgResearch’s genetically modified High Metabolisable Energy (HME) ryegrass has shown promise for reducing methane emissions.

Only a small-scale trial with sheep on a restricted diet over 11 days was possible, given the requirement to grow the HME ryegrass in specialised containment glasshouses and having to ensile (preserve) multiple harvests over 18 months to obtain enough for the feeding trial.

However, scientists working on the HME ryegrass programme are encouraged by the results from the trial.

Measurements taken from sheep fed ensiled HME ryegrass (with its increased lipid content) showed methane emissions were reduced 11 per cent when expressed as a percentage of GEI (Gross Energy Intake). When expressed as grams of methane per kilogram of DMI* (dry matter intake), the reduction was 7 per cent. 

There was a trend for feed intake to be reduced on the HME treatment, which is in line with previous research where AgResearch scientists supplemented lipids to sheep grazing ryegrass. In this previous work, the lowered intake did not result in a reduction in animal performance, raising the possibility that an unrestricted diet of HME ryegrass may have a greater reduction in methane emissions due to a reduction in methane per unit of intake, and reduced intake. This would need to be experimentally tested.

The recent feeding trial was supported by the New Zealand Agricultural Greenhouse Gas Research Centre, Grasslands Innovation Limited, and AgriZeroNZ.

The HME ryegrass, developed by AgResearch scientists with the support of Grasslanz Technology, PGG Wrightson Seeds and DairyNZ, is achieved by adding two modified plant genes to increase the lipid content in the leaf. In the feeding trial, the sheep were fed ryegrass with almost double the lipid content compared to the unmodified ryegrass silage (4.4% vs. 2.3%, respectively).

In addition to a reduction in methane, the higher level of lipid in HME ryegrass is also expected to result in an increase in the nutritional value, which has the potential to boost farm productivity. Also, in 2023 the research team published research showing that HME ryegrass can reduce emissions of nitrous oxide – another potent greenhouse gas.

The HME ryegrass has been developed and grown in labs and glasshouses in New Zealand, in line with the country’s regulations. When grown in paddocks, it will have the distinct advantage of being available to livestock to routinely graze, as opposed to being fed as a supplement.

The programme is currently seeking investment to fund the next stage of the work toward commercial handover to its seed company partners. Further research and trials of the HME ryegrass may take place in New Zealand or Australia depending on funding arrangements.

* Dry matter is the weight of the ryegrass after all moisture has been removed.

High Condensed Tannin White Clover

A programme in which white clover is being modified for the benefit of farm production, animal health and the environment, is working towards a trial where the clover will be fed to animals for the first time.

The High Condensed Tannin (HiCT) white clover has been modified by scientists to boost the level of condensed tannins present in the leaves. Condensed tannins occur naturally in the flowers of white clover and in other species such as grapes, tea and many other components of the human diet.

In white clover — an important component of pastures in New Zealand — these condensed tannins offer significant promise for reducing environmental impacts from livestock farming while improving both animal health and production.

AgResearch scientists are working with partners PGG Wrightson Seeds and Grasslanz Technology to genetically modify the white clover with a gene taken from another species of clover to increase the condensed tannin content in leaves.

The research results seen to date suggests a reduction in methane emissions of 15 per cent from livestock is achievable.

Growing trials with the HiCT white clover have been taking place in Australia, in both New South Wales (NSW) and Victoria, with the plants being studied for properties such as growth rates, condensed tannin content and weediness.

A focus in 2025 is to generate sufficient seed to grow enough clover to conduct a sheep feeding trial in 2026, which will be the first animal feeding trial for the programme.

Measurements will be taken through the feeding trial to assess the impacts on methane emissions from the animals.

Seed has been produced in Victoria to grow the clover for the animal feeding trial in NSW, and the programme will be engaging with the Australian regulator – the Office of the Gene Technology Regulator (OGTR) – as it
moves to the feeding trial stage.

Results from this feeding trial will help the programme plan further research and a path to commercialisation of the HiCT white clover.

Gene edited endophytes

AgResearch has paused an application for an outdoor field trial of ryegrass containing gene-edited endophytes in New Zealand as it waits to see what pathways could be available through new legislation before Parliament.

As reported in the last Pasture Biotechnology update, a process was started last year that was expected to lead to a full application to the Environmental Protection Authority seeking permission for a contained outdoor field trial.

However, the Gene Technology Bill – which was introduced in December and will potentially come into force later this year – is likely to provide a different process for trialling these gene edited endophytes than that which exists in current regulation.

These Epichloë endophytes live inside ryegrass and form a mutually beneficial relationship. Natural substances released by the endophytes deter insect pests from eating the ryegrass and improve plant growth and persistence, which collectively results in a reduced need for chemical pesticides and increases efficiencies in milk and meat production for New Zealand.

The challenge has always been that some endophytes that protect ryegrass against pests also produce toxins that can be harmful to the livestock which feed on the ryegrass, causing heat stress or a disease called ryegrass staggers. AgResearch scientists, supported by commercial partners PGG Wrightson Seeds and Grasslanz Technology, have identified in the lab targeted changes to the DNA of selected endophytes via gene editing that result in either greater plant protection or less harm to livestock.