A trial project in Waikato aiming to find a possible link between bulls' genetics and the amount of methane they produce is showing promise, scientists say - though more data is still needed to confirm early findings.
If a link is found it could lead to farmers being able to play a role in combating climate change by allowing them to breed cows that emit less methane.
The project is being run by breeding companies Livestock Improvement Corporation (LIC) and CRV, which together sire 90 percent of New Zealand's dairy herd through their artificial breeding bulls.
Dr Richard Spelman, LIC's chief scientist says a pilot trial measuring the feed intake and methane emissions - in the form of burps - of 20 young bulls gave good results. Now, researchers are set to progress to a larger study involving 300 young bulls.
"Methane production primarily relates to how much an animal eats," Dr Spelman said on Monday.
"We've accounted for this and we're still seeing variation which suggests genetics plays a role in a dairy bull's methane emissions - now we need more data to prove it."
Dr Spelman said if the project is successful it will give farmers another tool to reduce their on-farm emissions.
"If this genetic link is confirmed, farmers will ultimately be able to breed low methane-emitting cows from low methane-emitting bulls."
Despite the early success, Dr Spelman said scientists needed to take into account various aspects when breeding animals, not just the level of methane they emit.
"It's really important that we understand the genetic relationships between methane and traits like milk production and fertility. We don't want to find we are selecting against methane and inadvertently breeding cows that are less fertile," he said.
The project follows similar research into how to breed sheep that emit less methane.
Harry Clark, director of the New Zealand Agricultural Greenhouse Gas Research Centre, which is helping to fund the project, said success in that field had led to optimism in the dairy industry.
"We have been highly successful in New Zealand in breeding low-emitting sheep and this preliminary work with the bulls is a positive sign that we should be able to achieve the same for the dairy sector."