IN a new project, researchers from Aarhus University in Denmark — in cooperation with Organic Denmark and a number of commercial partners — will examine whether adding organic oregano to cattle feed can reduce the production of methane in the rumen and, thus, emissions of methane gas.

When ruminants digest their feed, methane is formed as a natural byproduct of the microbial process in the rumen, and since methane is 25 times more powerful than carbon dioxide as a greenhouse gas, there is a need to devise methods to reduce such emissions from cattle.

Methane production can be reduced by, for example, adding fat or nitrate to the feed or by increasing the starch content and improving the feed quality. However, for organic dairy farmers, these remedies either are not permissible or are being used already, thus creating a need for other solutions.

"Oregano — especially the species Greek oregano (Origanum vulgare subspecies hirtum) — is known for its high content of essential oils and its antimicrobial effect, and the plant is a natural tool for reducing methane production in the rumen," said Kai Grevsen, project manager and senior researcher in the Aarhus department of food science. "The goal is to show that we can reduce methane emissions from dairy cows by up to 25% by adding oregano to the feed."

As part of the project, the researchers will initially test the effect of supplementing oregano to rumen-fistulated and intestinal-fistulated dairy cows in special methane chambers. Further, they will examine how the cows react to different amounts of oregano.

The four-year project will also investigate how best to grow organic oregano and whether to process the plant as hay or as silage.

"To succeed with the oregano project in practice, it is essential that we develop a product that has both a high yield and a high concentration of essential oils. We also need to develop an organic farming concept and breed new varieties with higher concentrations of the oils," Grevsen said, adding that he and his colleagues also collaborate with an organic herb producer who makes fields and a drying facility available for part of the experiment.

Climate-friendly milk. Although the climate is intended to be the main beneficiary of the project in the form of reduced methane emissions, the hope is that the project will also benefit arable land and dairy farmers.

Previous studies have indicated that oregano can improve the fatty acid composition of the milk, and project participants will be researching this aspect as well as the flavor of the resulting milk.

"It's also important to remember that the project is relevant not only for organic milk producers: Should the results be positive, they can be implemented on all cattle farms — conventional and organic — so there is a really large potential," Grevsen said.

Volume:88 Issue:03