12 November 1999

Research backs official pledge to reduce methane

By Emma Penny

ENVIRONMENTAL targets agreed by the government at the Kyoto summit may yet have an effect on farming.

Researchers are looking at how much methane stock produce, and how it can be reduced.

Work funded by MAFF at ADASs Feed Evaluation and Nutritional Sciences unit at Stratford-upon-Avon, Warks, is focusing on the greenhouse gas, methane.

Researcher Angela Moss explains that the government has undertaken to cut emissions of greenhouse gases, and, therefore, must achieve it.

"Methane is a potent greenhouse gas – 15-30 times more so than carbon dioxide. It also stays in the atmosphere for only 10 years, compared with carbon dioxides 100 year lifespan, which means cutting methane production now will have a quicker payback in environmental terms."

Work over the past 10 years has looked at how much methane stock produce, while more recent research has considered how much methane is produced over an animals lifetime.

"We looked at how much calves produced too, and found that they produced a significant amount, although obviously much less than a cow. We also studied whether a heifer calving at two years old in autumn or spring made any difference. Results of this research should be available within the next six months."

With research proving that cattle – and sheep – contribute a significant amount of methane to the atmosphere, Dr Moss and researchers at the Rowett Research Institute in Aberdeen started to look at feed additives which might reduce emissions.

"We found that substances known as propionate enhancers can cut methane emissions by about 20% in lab tests."

She explains how these work: "In a cows rumen, carbon dioxide and hydrogen are used by bacteria to produce methane. But hydrogen could be diverted into producing something more useful – propionate.

"The idea is to feed animals a precursor to propionate so hydrogen can be diverted to produce propionate, a volatile fatty acid. This is converted in the liver to glucose, providing an additional energy source for cows. We believe providing propionate precursors may also improve fibre digestibility as a result of changing rumen microbiology."

Trials are now looking at whether lab results can be replicated in sheep. But Dr Moss believes that if feeding propionate enhancers can improve energy availability and fibre digestibility, producers might be keen to include them in rations for reasons besides their environmental benefits.

"If these benefits mean their inclusion is cost neutral, compounders and producers may be keen to use them, and they could also be used in beef and sheep rations when they are fed concentrates. But if there is a cost to using them, it may be that government insists they are included," she warns.

Other lab work is considering whether emissions could be cut by boosting the populations of specific micro organisms which naturally occur in the rumen, says Dr Moss.

Methane oxidisers are micro organisms that occur naturally in the rumen in low numbers. Increasing their population significantly could cut methane emissions, she believes.

"These micro organisms oxidise methane, converting it to acetate, a volatile fatty acid which is absorbed by the rumen and used by the cow. While most people would argue that the rumen is anaerobic – does not contain oxygen – cows will naturally take in oxygen when they eat or drink, so theres enough oxygen for the micro organisms to convert methane successfully."

Increasing the population of methane oxidisers is likely to depend on producing them in a fermenter and feeding them as a probiotic. This should boost their rumen population sufficiently, allowing an 8-10% drop in methane production.

Besides methane oxidisers, researchers are also looking at other micro organisms known as acetogens. These convert carbon dioxide and hydrogen to acetate.

"Like methane oxidisers, acetogens exist in the rumen in small numbers. Providing them as a probiotic could boost their population enough to cut methane emissions by 8-10%."

Both micro organisms are being investigated, and are undergoing screening trials both at ADAS and the Rowett. If successful, the next move is to find how to produce them in a lab fermenter, then feed them to sheep to see if lab results can be replicated in animals. &#42

METHANE CHALLENGE

&#8226 Kyoto agreement.

&#8226 Must cut methane emissions.

&#8226 Feed additives could help.