The issue of enteric (from intestines) methane (CH₄) emissions produced by ruminant livestock is gaining local and global interest due to methane being a powerful greenhouse gas and ruminants being a significant source of emissions. In the absence of measurements, prediction models can facilitate the estimation of enteric methane emissions from ruminant livestock and aid investigation of mitigation options. In Southern Australia, the management of the feedbase in low rainfall mixed farming systems through addressing ‘feed gaps’ – times of year during which the supply of forage is insufficient to meet livestock demand; is a key practice change which has the potential to mitigate methane emissions, particularly from sheep.

The aim of this trial was to evaluate pasture/forage options with a potential to fill the late-spring and early winter feed gaps and to measure comparative animal production and feed quality in response to current and improved forages. Methane output (gCH₄/day) was simulated using the GrazFeed model.

The GrazFeed decision support tool is a component of the GRAZPLAN decision support project for Australian grazing enterprises developed by CSIRO to help graziers improve the profitability of livestock production through more efficient use of pastures and supplementary feeds. It does this by predicting the intake of energy and protein and their use for maintenance and production (Freer et al., 1997).

• Grazing vetch and lucerne can be used as a management strategy to improve lamb dry matter intake and growth rates during the late spring and early winter feed gaps.
• The Grazfeed decision support tool has predicted that while both legume forages (vetch and lucerne) will increase methane output (gCH₄/day), there is a reduction in methane output per unit of animal product (gCH₄/day/100gADWG).
• Moisture limitations can affect herbage production of lucerne, which in turn reduces the chances of growing lambs to achieve the full potential dry matter intake in low rainfall mixed farming systems.