The trial showed an 11% methane reduction in sheep fed HME ryegrass. Photo / 123RF
The trial showed an 11% methane reduction in sheep fed HME ryegrass. Photo / 123RF
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.
This was due to 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 that methane emissions were reduced by 11% when expressed as a percentage of GEI (Gross Energy Intake).
When expressed as grams of methane per kilogram of dry matter intake (DMI), the reduction was 7%.
Dry matter is the weight of the ryegrass after all moisture has been removed.
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.
This raises 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 New Zealand Agricultural Greenhouse Gas Research Centre, Grasslands Innovation Ltd, and AgriZeroNZ supported the recent feeding trial.
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.
A sheep in AgResearch's High Metabolisable Energy (HME) ryegrass feeding trial. Photo / AgResearch
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 increase 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 nitrous oxide emissions – 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, instead of being fed as a supplement.
