More than 100,000 compounds have been screened, and many thousands tested in laboratory experiments over the past several years.
To date five compounds, selected as the most promising options, had been tested on sheep and resulted in reductions of methane emissions from 30 per cent to more than 90 per cent.
Dr Rick Pridmore, the consortium's chairman and steering group member of the Manawatu-based New Zealand Agricultural Greenhouse Gas Research Centre, said the successful tests of methane inhibitors was news Kiwi farmers could "get excited about".
"The results are significant for two reasons. First, because they work on livestock consuming a grass-based diet and, second because the short-term trials showed such dramatic results," he said.
"It must be stressed that these are early days. Further trials are needed to confirm these compounds can reduce emissions in the long term, have no adverse effects on productivity and leave no residues in meat or milk.
"We are already looking to engage with a commercial partner and, all going well, we could possibly see a commercial product within five years."
Methane inhibitors were only one of several options that New Zealand scientists were pursuing to help reduce greenhouse gas emissions from agriculture, Dr Pridmore said.
Other approaches included breeding, developing a vaccine and specific feeds to reduce methane emissions, exploiting natural plant properties to reduce nitrous oxide emissions, and increasing the amount of carbon stored in pastoral soils.
"Breeding for reduced methane emission is progressing very well. We have shown that the trait is heritable and indications to date show no negative production impacts. The difference between high and low emitters currently is about six per cent.
"This means sheep farmers should have access to breeding value information in about two years that allows them to select for animals with lower methane emissions than the average sheep.
"Work on cattle is only starting, but based on lessons we have learnt from sheep, we hope that cattle breeding values will follow within five years."
The research was funded by the jointly industry and government backed consortium and the wholly Government-funded New Zealand Agricultural Greenhouse Gas Research Centre.
Q&A: Dr Harry Clark, New Zealand Agricultural Greenhouse Gas Research Centre
How do ruminant animals like sheep and cows actually produce methane?
"It comes from the breakdown of feed. The feeds break down in the rumen, producing carbon dioxide and hydrogen, and there is a specialised group of micro-organisms which utilises the hydrogen and carbon dioxide and makes methane. This natural process has been occurring in ruminants for millions of years."
How would these newfound compounds work?
"They basically stop the activity of the micro-organisms that are converting the carbon dioxide and hydrogen to methane. It's very simple - it kills them or severely suppresses their activity."
How promising do the early results look?
"I think what we have to do is recognise that we are at an early stage, but this is a very strong scientific breakthrough in the sense that we now have identified some compounds that when fed to animals, reduce emissions between 30 and 90 per cent. But these are short-term animal trials and now have to be repeated in longer-term animal trials, because sometimes, products may work for a few days and not work in the longer term. And we have to check they are safe for the animals and safe for the consumer."
