Best choice shrub and inter-row species for reducing emissions

Summary

​Grazing systems based on shrubs and pasture species that are selected for their nutritive value and anti- methanogenic bioactivity offer a practical means to reduce methane emissions and emissions intensity from grazing livestock.

The results from this study support the concept of using perennial shrubs in a whole-farm system as a means of improving productivity whilst also improving methane emissions intensity, and also reducing the risk of inadequate feed during autumn.

Objectives

The objectives of this project were to:

• quantify the effects of grazing shrub and pasture inter-row species that exhibit low methanogenic potential in vitro on livestock production and methane emissions in the field
• establish commercially-available pasture species (or 'pipeline' species if sufficient quantities exist) with lower methanogenic potential in the inter-row of an existing shrub site and in a pasture-only system.

This data will fill a research gap necessary for the design of CFI methodology.

Key findings

• Sheep grazing shrub-based systems without supplementary feeding during autumn gained at least twice the weight of sheep grazing pasture with conventional amounts of supplementary feeding with grain.
• The sheep grazing shrubs also had a lower methane emissions intensity and produced less methane per unit of energy intake. This result was replicated in a modelling analysis, which also demonstrated that over a 12-month period, sheep that graze shrubs in autumn, have a better body condition which enables them to require less supplementary feeding over the year.
• The results from this study support the concept of using perennial shrubs in a whole-farm system as a means of improving productivity whilst also improving methane emissions intensity, and also reducing the risk of inadequate feed during autumn.

Benefits to industry

The results from this research demonstrated that native shrubs can improve animal productivity by offering an alternative to supplemental feeding with grain during autumn. Sheep that grazed a shrub-based system achieved greater liveweight gains than sheep that grazed conventional pasture with grain.

MLA action

MLA continues to investigate shrubs for productivity benefits and methane mitigation potential for livestock systems in Australia through the Emissions Avoidance Partnership.

Future research

Little is known about the health impacts a shrub- pasture system can have on livestock, which may also improve productivity and production efficiency because healthy animals are usually considered more productive.

It would be beneficial to understand more about the health status of sheep when they graze such a system and the follow-on impacts this has on overall productivity.

At the same time, measurements of the full value of shrubs including below and above ground biomass, shade and shelter, nutrient and water flow in those systems would add to our picture of the overall benefit shrubs can have on productivity but also on carbon balance.