Statistics have been giving us a bum steer when they state how much cattle methane emissions contribute to global warming, a new study shows.

That’s because mathematical equations used to predict cows’ methane emissions are inaccurate and don’t take into account factors such as dietary changes, said Jen­nifer Ellis, lead author of the study and a PhD student at the University of Guelph.

When cattle burp up their cud, they discharge methane with it, due to microbial fermentation occurring in their complex stomachs.

“Diet can change CH4 (methane) emissions quite a lot,” she said. “As a crude comparison, a typical dairy cow will produce as much (in carbon dioxide) equivalents per month as a mid-size car does travelling 800 kilometres per month. Changes (of) two to 12 per cent of the energy intake can be the difference between that cow being a compact car and an SUV or truck,” she added.

When an equation calculates the quantity of methane emissions on one farm, it can’t be used to accurately determine how much greenhouse gas is created worldwide because there is so much difference in cattle diet around the world and from farm to farm.

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