AgResearch scientists and US researchers are one step closer in their work to reduce methane emissions from sheep.
They have identified microbial differences in the rumens of sheep with high or low methane emissions.
The work is part of a Global Partnerships in Livestock Emissions Research project and has been carried out by the Rumen Microbiology team at AgResearch Grasslands in Palmerston North, and at the US Department of Energy's Joint Genome Institute (JGI) in San Francisco, California.
Methane belched from sheep and other ruminants accounts for around 28% of global methane emissions from human-related activities. It is produced in the rumen by microbes called methanogens and the work targeting these organisms is aimed at reducing methane emissions from ruminants.
AgResearch scientist and project leader, Dr Graeme Attwood says the results, which have just been published in the top-ranking journal Genome Research, are one of the first major findings of the four-year project.
"The study used the large sequencing and data analysis capabilities of the JGI to look at the occurrence, abundance and expression of methanogen genes between low and high methane-emitting sheep identified from flocks in New Zealand," he says.
"These analyses showed that, although the relative abundance of genes did not differ between the low and high methane groups, the expression of genes involved in the metabolic pathway leading to methane formation were significantly elevated in methanogens within the rumens of high methane-emitting animals."  He says this discovery helps explain the methanogen involvement in this animal trait, and it is likely that further detailed analysis of the large sequence datasets will uncover differences in other rumen microbes which also contribute.
 The study is funded through the New Zealand government in support of the objectives of the Global Research Alliance on Agricultural Greenhouse Gases and its Livestock Research Group, and builds on previous work by a combined NZ Agricultural Greenhouse Gas Research Centre and NZ Pastoral Greenhouse Gas Research Consortium programme in which a large number of sheep have been screened to identify naturally low or high methane-emitting animals.
This programme aims to breed sheep for New Zealand farms which are low methane-emitters but also maintain their ability to reproduce and retain or improve their meat and wool production.
The microbial gene expression differences discovered in the study help define the methane trait in sheep and will assist in the selection of future low methane flocks.
"Understanding the microbial composition of a low methane animal and how its rumen works, will enable us to focus on targeting the methanogens directly using complementary approaches such as drenches, slow release boluses or specialised forages and supplements," says Dr Attwood.
The paper "Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome" has been published this week in the journal Genome Research
About AgResearch: AgResearch is New Zealand's largest Crown Research Institute and focuses on supporting the country's pastoral sector through scientific research and innovation.
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Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome
06/06/14 | Shi, W., C. Moon, et al. (2014). "Methane yield phenotypes linked to differential gene expression in the sheep rumen microbiome." ...
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