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Methane: The proof is in the feces


June 8, 2011
By Manure Manager

manure04June 8, 2011 – Scientists
could have a revolutionary new way of measuring how much of the potent
greenhouse gas methane is produced by cows and other ruminants, thanks to a
surprising discovery in their poo.

June 8, 2011 – Scientists
could have a revolutionary new way of measuring how much of the potent
greenhouse gas methane is produced by cows and other ruminants, thanks to a
surprising discovery in their poo.

Researchers from the University
of Bristol
and the Teagasc Animal and Grassland Research Centre in Ireland,
have found a link between methane production and levels of a compound called
archaeol in the feces of several foregut fermenting animals including cows,
sheep and deer.

manure04  
   

The compound could
potentially be developed as a biomarker to estimate the methane production from
domestic and wild animals, allowing scientists to more accurately assess the
contribution that ruminants make to global greenhouse gas emissions.

 “When it comes to calculating carbon budgets, there is
currently a lot of uncertainty surrounding animal methane contributions,
particularly from wild ruminants,” said co-author Dr. Fiona Gill, who conducted
the work as a postdoctoral researcher at Bristol and now works at the
University of Leeds.

“We’re quite good at
measuring man-made CO2 emissions, but techniques to measure the animal
production of methane – a much more potent greenhouse gas – have serious
limitations.

“If we can identify a
simple biomarker for methane production in animal stools, then we can use this
along with information on diet and animal population numbers to estimate their
total contribution to global methane levels.”

Cows, sheep and other
ruminants are thought to be responsible for around one-fifth of global methane
production but the precise amount has proved difficult to quantify. Methane
production from animals is often measured using respiration chambers, which can
be laborious and are unsuitable for grazing animals.

Archaeol is thought to
come from organisms called archaea, which are symbiotic or friendly microbes
that live in the foregut of ruminant animals. These microbes produce methane as
a by-product of their metabolism and this is then released by the animal as
burping and flatulence.

“We initially detected
archaeol in the feces of several foregut fermenters including camels, cows,
giraffes, sheep and llamas, said primary investigator Dr. Ian Bull of Bristol’s
School of Chemistry. “We then expanded the study to evaluate the quantities of
this compound in the feces of cows with different diets.

“Two groups of cows were
fed on different diets and then their methane production and fecal archaeol
concentration were measured. The animals that were allowed to graze on as much
silage as they wanted emitted significantly more methane and produced feces
with higher concentrations of archaeol than those given a fixed amount of
silage, supplemented by concentrate feed.

“This confirms that
manipulating the diet of domestic livestock could also be an important way of
controlling methane gas emissions.”

The work was carried out
at the University of Bristol and the Teagasc Animal and Grassland Research
Centre
in Ireland.

The research is published
in the journal Animal Feed Science and Technology.


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