putting a match to a cows arse
when is about to fart
then stand back and admire the your just work as the cows explodes.
"(California) A dairy worker who heard that bovine flatulence was largely composed of methane, and potentially explosive, decided to apply the scientific method to the theory. While one of his contented cow charges was hooked up to the milking machine, he waited for the slight tail lift which dairy workers know signals an impending expulsion, generally something to avoid. Our hero struck a match. His satisfaction at seeing the resulting foot-long blue flame lasted mere seconds, volia you have a exploding cow"