It is claimed cows produce 500 litres of methane a day
Some cows could swap the field for the cattle shed in the future so farmers can collect the methane they produce.
A new report claims greenhouse gases produced by agriculture could be cut dramatically if farmers altered the way they farmed.
It says emissions will fall if woodland is expanded and energy, fertilisers and manure are used more efficiently.
The report was written by the Land Use Climate Change Group, which was set up by Rural Affairs Minister Elin Jones.
It is claimed that cows produce 500 litres of methane a day, equivalent to 10 tonnes of carbon dioxide a year.
Ms Jones set up the group, chaired by Professor Gareth Wyn-Jones, last year to consider how agriculture and land use can reduce climate change and adapt to it.
In the longer term, the report recommends development of a more radical approach where cattle herds are housed and methane emissions are captured.
But officials from the assembly government said the technology to capture the gas had not been developed yet.
Another of the recommendation in the report is to introduce anaerobic digestion to reduce the methane emissions produced by animals.
Professor Wyn-Jones, founding director of the Centre for Arid Zone Studies at Bangor University, said: "It is our judgement as a group that the components of the recommended scenario offer a positive way forward which will not only achieve a major cut in net emissions by about 2040, but also will contribute to the sustainability of rural Wales by generating additional income streams including from micro renewable energy generation."