I have been warned that pigs will OD on salt and kill themselves.
I'm here to say: not so!
I imagine its possible that if you mixed salt and yummies (feed, molasses) etc, a pig could OD on that. But I've been using Salt Blocks (plain white, mineral mix, and selenium, free chocie [michigan soils are sel. deficient]) for quite awhile. Adequate mineralization of the pigs is one of the factors that depresses rooting, and pigs salt intake hikes considerably as their diet switches from grains (low potassium) to vegetation (high potassium). Potassium must be in a 3-way balance with sodium and chloride (why cows need so much salt)
They chew and slobber on those things.
I tried mineralizing pigs with kelp, but free-choice they kelp you into bankruptcy. I give them a bit now and then.
We just put out mineral blocks that contain salt and let the hogs decide when and how much of it they eat.
A sow increases her intake when she is pregnant and keeps up her intake until the babies are weaned.