I've known lots of people to do it over the years. Never believed in it until a neighbour that raised Limo's had a bad batch of scrappin' jugheads. Several got hurt all in one week, so he bought a couple donkeys somewhere, threw them in, and we grabbed a beer to watch the spectacle. As soon as bulls started at it, one donkey ran right into the bunch of them and started spinning around kicking out at everything and everyone. Some got it in the guts, some in the legs, some in the head. After a couple of days, bulls were happily grazing alongside 2 content donkeys.
I've seen billy goats do the same thing. Except around here goats disappear in the dark and reappear in coyote droppings. With a donkey, coyotes appear in the dark, and reappear in magpie droppings.