If there is plenty of feed there should really be no need to chew wooden railings but yiu know pigs....they will because they can and it is a pain when they do. I put in new drinkers jsut recently and left one exposed at the back thiking it would be alright....... not so, had to cover it with a piece of sheeting to stop them totally wrecking it. They have a good wallow and a good drining system too.