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Cows on diet emit 40 per cent less methane

Wednesday 16 Sep 20


Anne S. Meyer
DTU Bioengineering
+45 45 25 25 98


Kristian Barrett
DTU Bioengineering


Methane—CH4—is a greenhouse gas. Although it is formed naturally by microbial degradation of organic matter, methane has a more negative impact on the greenhouse effect of the atmosphere than carbon dioxide. Methane’s share of the greenhouse effect is estimated at 15 per cent overall, and contributions from ruminants—mainly cows—are significant.

Read more about Aarhus University’s research on cows’ production of methane

Feed changes can reduce methane formation from microorganisms in the cow’s paunch and reduce cows' emissions by 40 per cent without compromising milk yield.

This is shown by the preliminary results of an experiment with 12 cows conducted in climate chambers at Aarhus University.  Researchers at Aarhus University have designed the feed experiment, while DTU has supplied analyses of all the genes in the microorganisms in the cows’ paunch. These analysis data now paint a picture of the changes in the microbiome of the paunch that explain the reduced methane formation. The analyses are based on changes in 263 billion DNA base pairs in which the DTU researchers have analysed changes in connection with the feed changes.

“We can see that it has a significant positive effect on reducing methane formation if the amount of clover grass and maize silage is reduced, and these feed components are instead replaced with straw and wheat. We’ve been surprised that the conventional feed results in the formation of large quantities of methane, because it especially gives good growth conditions for the microorganisms that live on breaking down dietary fibres containing complex carbohydrates such as pectin and xylan,” says Anne S. Meyer Professor at DTU Bioengineering.

"It is quite clear now that much of the feed that cows normally receive increases methane formation. So the new data mean that the feed mixtures given to dairy cows should be reassessed to reduce methane formation"
Professor Anne S Meyer, DTU Bioengineering

The results from the genome analyses of the cows’ microbiome are still only at a preliminary stage, as the DNA analyses have been performed on paunch fluid. The new data were recently presented at a meeting of the research group. The project is a large multi-year project, funded by the Danish Milk Levy Fund. Based on the preliminary genome analyses of the cows’ microbiome, the researchers will conduct new experiments for more in-depth identification of the microorganisms which are of greatest importance to the reduction of methane production in the cows’ paunch.

Anne S. Meyer explains that the analysis of the large data volumes is only possible because the researchers at Aarhus University have been able to create a completely unique, controlled test design in which 12 Holstein cows are divided into three groups, each of which is given different feed types. The cows are first balanced on the feed for three weeks, and are then placed in climate chambers, where methane development and milk production are measured very precisely.

“We’re particularly focused on the enzymatic degradation processes that occur via the activity of the microorganisms in the cow’s paunch. It is quite clear now that much of the feed that cows normally receive increases methane formation. So the new data mean that the feed mixtures given to dairy cows should be reassessed to reduce methane formation,” says Anne S. Meyer.

According to Anne S. Meyer, the new research results and analyses open up for a completely new approach to feed given to cattle. Based on the mapping of more than 900 genomes in the cows’ microbiome, the researchers can now begin to make recommendations.

“What happens in the cow will not remain a black box, as new information has emerged about the mechanisms in the microorganisms of the cow’s paunch which cause these emissions. And it gives us brand-new tools in the toolbox for lowering methane emissions from cows,” says Anne S. Meyer.

She sees great opportunities for Danish agriculture to show the way to more sustainable feed strategies for cattle, which can pave the way for a large methane reduction when the experiences from the study gain ground in large cattle-raising countries in South America and the United States.

Together with the researchers from Aarhus University and several of the other project partners—including LLa Research & Advisory and the University of Copenhagen—researchers from DTU will now continue the work to understand exactly which feed elements are good and bad, respectively, in connection with cows’ methane emissions. On this basis, they will develop several strategies aimed at reducing methane emissions from ruminants.  

8 MARCH 2021