It's seems according to the great lord of all things vetinary, James Herbert, that the way they work the bulls is to have a cow on heat (any cow will do a bit like humans really) introduce the bull to the cow, (hello bull this is a cow), then just as he's about to mount they shove a water filled ring and a condom onto the bulls penis, however one farmer they asked to fill the ring used boiling water, (he treated it like a hot water bottle!). The bull wasn't amused [no surprise there eh?]
