does anyone give their stud dog anything special before a mating or after i.e. feed? or not fed? or big feed after ?

Nope, exercise is exercise.  I wouldn't mate him on a full stomach or feed him too soon after.  I usually make sure he has plenty of water beforehand as he seemed to get really thirsty during but again, I wouldn't over-do the water at the mating either.
My boy used to be so content after a mating that he wouldn't care what he got for his tea that night!lol

Just to add, I would be worried about bloat as mine was a deep-chested breed but I suppose that would depend on what your stud is.  But I don't imagine it's very comfortable doing the deed with a full stomach?

Someone i know feeds extra the week following up to the mating to compensate for not eating through stress with a visiting bitch. She tends to have visiting girls stay over as she has these dogs visit from europe specially for matings

cant say he gets stressed at all,and certainly dont feed  before or after mating for a couple of hours at least, but he,s always ready for his food

we dont feed him till hes done the deed and then wait 2h.