I find it quite amazing how, on the whole, adept most animals are, at not eating/swallowing anything but food and spitting out the other stuff. I've seen horses, pigs and sheep cleverly spit out stones etc. Being realistic they are bound to pick up "other stuff" in less clinical surroundings like fields.
I would say your biggest problem would be that pigs will dig for that morsel that escaped them and make a right mess of any area that is not solid, especially if it then gets wet and puddles. Road plannings are very good as they bond together.