Methane control goes native

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Native plants may lower greenhouse gas emissions in their role as feed for sheep, according to University of WA research.

With two thirds of Australia's agricultural emissions coming from enteric methane, produced during rumen fermentation in ruminants such as sheep, PhD candidate Xixi Li wanted to study the role of feed manipulation in lowering the level of what accounts for about 10 per cent of national emissions.

To further pursue her PhD research on how the Australian native plant, Eremophila glabra, or tar bush, when consumed by sheep, reduces methane production in the rumen, Ms Li was one of two recipients of the 2011 Mike Carroll Travelling Fellowship. The other is fellow UWA PhD student Chelsea Fancote.

Ms Li and Ms Fancote this month attended the 8th International Symposium on the Nutrition of Herbivores in Wales, UK, where Ms Li presented a paper and discussed her UWA Institute of Agriculture (IOA) research with world leading scientists in the field of livestock production.

According to her PhD supervisor, UWA IOA animal production systems program leader Professor Phil Vercoe, her ultimate aim is to develop more diverse forage bases for grazing ruminants in Australia, including plants such as E. glabra.

"Xixi has already demonstrated that tar bush has dose related, persistent, modulating effects on rumen microbes and she will use this exciting finding to design an experiment where she will feed tar bush to sheep in respiration chambers to accurately measure methane emissions and also to ensure the effects she's observed in the laboratory are replicated in the animal itself," he said.

After screening more than 100 native plants as feed supplements to improve feed intake, digestibility and rumen fermentation, Ms Li and her colleagues selected E. glabra, a shrub that tolerated harsh growing conditions and could provide livestock fodder in WA, even in drought.

"I have found an optimal inclusion level of E. glabra, which can reduce methane production by about one third, while not adversely affecting general rumen fermentation," she said.

"It seems that with no effect on total volatile fatty acid concentrations, the major end products of rumen microbial fermentation, E. glabra alters the diversity and activity of ruminal microbes."

Ms Li believed that if methane production could be reduced, while increasing total volatile fatty acid production, animal production could be improved.

However, she stressed that E. glabra only needed to make up a part of the animal's diet to have these effects and its value would be as a component of a more diverse mixture of plants for grazing.

"This would give us a solid base to reduce greenhouse gas emissions from ruminants and contribute to developing green, sustainable and profitable grazing systems for WA sheep," she said.

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