I personally would never run a boar with any other piglets, weaner's growers etc, at the end of the day he is a boar and the "top man" and should never be 100% trusted. If you have a outdoor system running with him your sows to serve them is ok, although personally I don't do this, if he is a young boar he can pester sows to death and also he may get a leathering of a sow that will put him off mating or over stretch himself and do the same, I like to take the sows to him and see them served so you know the exact date you are due to farrow instead of guess work. Keep him in a next door pen or at very least where he can see or smell other pigs is a must, this has the effect of keeping him interested he'll "talk" to the other pigs and his pheromones in the air will bring your gilts/sows in season.