Now, up to a week ago I believed too that is was cow farts that we were dealing with, but there was a guy on the radio who was adamant that it wasn't from that end that the gas imitated.
It was from some of the many stomachs that the gas returned. I'd love to know which end the cows emit. As a one time farm boy I'm reasonably familiar with cows and I've no recollection of foul breath.