Great Topic lol. Well I have bad luck... cause all my three geldings do it. But they save it, to when my face is almost hozilontal with there bum hole lol
. They do it, either when im brushing there bums, or braiding there tail. And for some reason they always have a bit of wind everytime... they don't fart when my daughters are riding them, but as soon as your close to their bottom...they let one rip. So yes, if anyone has a theroy behind this... I..along with others would love to hear it lol!