Methane from cattle damages the environment
The EU-funded project led by scientists at the Rowett Research Institute in Aberdeen could create a "safe, green alternative" to existing additives such as antibiotics.
Researchers believe that plant extracts could increase the efficiency of livestock production, help the environment and slow the spread of antibiotic resistance in human infections.
Natural plant extracts contain essential oils which have been found to have a beneficial effect on bacteria in the cow's rumen - the first section of the stomach.
Dr John Wallace, head of the microbial metabolism research group at the Rowett, said: "We know that the release of methane from ruminants is extremely damaging to the environment.
"We believe our work has the potential to halt this increase and help stabilise the environment by taking a natural route to improved rumen fermentation.
"At the same time, we believe that the current growth in antibiotic resistance in humans, part of which is generally accepted to be linked to the use of antibiotics in animal feeding, could also be reduced by quite a substantial amount."
Dr Wallace said that the natural oils have a pleasant smell.
Significant improvement
He said: "Although the effects on the manure are small, the distinctive aroma is very obvious, indeed pleasant, in the building used to house the cattle."
The Rowett's interest in the potential feeding value of new plant species is rooted in 20 years of work with the International Livestock Research Institute (ILRI) in Addis Ababa, Ethiopia.
Scientists have found that foliage from a tree species in Africa appears to suppress the protozoa which inhabit the rumen.
Dr Wallace said that this suppression leads to a "significant improvement" in production efficiency which resulted in less methane and more benefit to the environment.
The 'novel plants' research project, of which the Rowett is the co-ordinating body, involves academic and commercial partners in Switzerland, Ireland, Spain, Germany and the UK.
The work is funded by the EU at £1.2m (1.94m Euros), plus a contribution of £85,000 (137,640) Euros from the Swiss government.