The 25 September 2004 issue of New Scientist reported this work, being done by the Commonwealth Scientific and Industrial Research Organisation in Perth, Australia.

Some scientists, performing
A review of global warming,
Have highlighted what ruminators do:
They generate – to be plain –
One fifth of global methane,
A greenhouse gas much worse than CO2.
At C.S.I.R.O.,
They have found a way to go:
They give the beasts a course of vaccinations
Which enters their interior
And kills off the bacteria
That generate their harmful eructations.
No-one’s asked the cows or sheep,
Or the company they keep,
Their views on this, or asked for their permissions.
But here’s what Daisy says:
“We haven’t changed our ways,
It’s you who’ve increased greenhouse gas emissions”.