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Maximum milk for minimum methane

By selectively breeding not only cows, but also their rumen bacteria, researchers intend to reduce the release of the greenhouse gas methane, while also increasing the effectiveness of the cow's milk and meat production.

2012.11.30 | Janne Hansen

Scientists will breed cows that burp less methane by, among things, breeding the cow's rumen microflora. Photo: Jesper Rais

Cows are fantastic. They can turn grass and other plant material – inedible by humans - into large amounts of food products such as milk and meat. This is an important quality when it comes to meeting the rising global demand for animal products.

Unfortunately there is a downside. Each time a cow burps – and ruminants do so frequently – it emits methane, which is one of the greenhouse gasses with the greatest global warming potential.

So what do you do? Can you breed some form of super-cow with a high feed efficiency and yield but with more appropriate burps?

Practically speaking, the idea is not impossible, provided one approaches the issue from several different angles. Researchers from Aarhus University know how to do just that, and are leading a new project focusing on reducing the methane emission from cows whilst increasing its feed efficiency through modern breeding.

Some of the angles from which the researchers are approaching the matter are modern genetics, rumen microbiology and analysis of burped air.

The methane from the cow is not its own

When a cow eats, it gets some help to digest the otherwise indigestible grasses and roughage from the micro-organisms that live in its rumen. Methane is a natural by-product of this microbial digestion. Beyond the cows’ methane-rich burps affecting the environment, the emission also constitutes an energy waste for the cow, with a direct, negative effect upon its feed efficiency.

Scientists have previously observed that there is a considerable variation between cows, both when it comes to their feed efficiency and their methane emission. Variations could be due to the cow's own genetic variations, their rumen bacteria and the interaction between the two.

As there are individual differences in which types of rumen bacteria the cow is hosting, there is the potential through breeding for shifting the composition of the rumen flora in the desired direction – not least because there seems to be a positive correlation between good feed efficiency and low methane emission.

- Our hypothesis is that there is a quantitative variation in the microflora of the rumen which is partially controlled by the cow's genotype – i.e. her genetic make-up. The micro-flora can thus be considered an independent organism with a quantitative variation, which interacts with the cow as the other organism, explains the leader of the project, senior scientist Peter Løvendahl from Aarhus University.

Sniffing machine and rumen probe
Approximately 1,000 cows from active farms and the Danish Cattle Research Centre are included in the project. The cows will barely notice that they are taking part in an experiment where the things being tested include how much methane they exhale and which kinds of bacteria their rumens contain.


The methane in the cows' breath will be measured whilst they are being milked in the automatic milking machine. For this purpose, a kind of ”sniffer” will be installed. The instrument is also used in Finnish hospitals to measure if incoming patients are intoxicated or have taken drugs.

Researchers will gain an overview of which bacteria the cow has in its rumen by taking samples of the gastric juices via a probe passed down the throat of the cow. This is a normal, non-invasive action which is already routinely used by vets in a variety of situations.

- Clarifying the complex connections between the cow's genetics, the genetics of her micro-organisms, the cow's feed efficiency and its methane emission will clear the way for reducing the methane production whilst optimising the feed efficiency. This would benefit the farmer's budget and the environment and is an area subject to much international attention, says Peter Løvendahl.

The four-year project has a collective budget of 14 million Danish kroner (€1.9m), of which the Danish Council for Strategic Research, Programme Commission for Health, Food and Welfare has provided 12.2 million kroner (€1.6m).

The project is a collaboration between a number of scientists from Aarhus University, the Technical University of Denmark, the Danish Cattle Research Centre and Viking Genetics. The project also involves researchers from the University of Vermont, USA, the Veterinary Medical University in Vienna and the United States Department of Agriculture, USDA.

The project is called ”REMRUM: Reduction of methane emissions from dairy cows and concurrent improvement of feed efficiency obtained through host genetics and next-generation sequencing of rumen microbiome”.

Further information: Senior scientist Peter Løvendahl, Department of Molecular Biology and Genetics, Aarhus University, Denmark, email: Peter.Lovendahl@agrsci.dk, telephone: +45 8715 7495.

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