i know desosect is only licenced for horses, but while at college our tutor used it on her hens, said it was the only stuff that worked. didnt pay much attention on how to use it though, just sprayed it on a bit, didnt like her hens how long do i have to use it for, where do i spray, does it kill on contact or go through the whole body and kill the mites? what is meat and egg withdrawl period? cheers