Desmanthus legume in livestock grazing pastures and its role in methane emissions

Summary

Methane is a greenhouse gas produced as a by-product of fermentation of feedstuffs in ruminants. Desmanthus is a tropical legume adapted to parts of northern Australia and studies have demonstrated that it can reduce the production of methane when incubated with rumen fluid.

This project was developed to test the hypothesis that increasing the amount of Desmanthus in the cattle diet would reduce the emissions of methane.

This project determined that methane production could be reduced by feeding Desmanthus to cattle and provided data to support a methodology allowing the avoided emissions to be traded in the carbon market.

Objectives

The objectives of this project were to:

• quantify the emissions of methane from growing cattle fed Desmanthus cultivars at a range of dietary inclusion levels
• develop methods for quantifying the reduction in methane emissions under commercial livestock grazing conditions.

Key findings

• Desmanthus, included at 30% of the diet, can reduce methane emissions from cattle by up to 10% when the nutritive value of the diet is low (5 to 8% crude protein).
• This response depends, however, on the conditions under which Desmanthus is fed and no reduction in emissions was observed when the diets were of higher nutritive value.
• For every percent increase in Desmanthus in the diet, the yield of methane drops by 0.066 g/kg DMI.
• Carbon isotope ratios in faecal samples offer a potential method for measuring intake of Desmanthus.
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Benefits to industry

This work will contribute to the development of a methodology that will allow cattle producers to earn revenue from carbon credits. It will further increase the adoption of Desmanthus as an adapted tropical legume for areas of Queensland, the Northern Territory and northern New South Wales.

MLA action

MLA is considering further investment in understanding the mode of action causing reduced methane production from livestock feeding on Desmanthus.

MLA is also working with the Commonwealth Government to support the development of a methodology that will allow cattle producers to earn revenue from carbon credits.

Future research

The findings of this research suggest further broad-scale assessment of the variability in methane reduction from Desmanthus pastures is warranted. This could be achieved using a field-based system to achieve scale of measurement.

Establishing the cause of reduced methane production is also required.