Interesting topic,alot of pro-cons.

We have put various salt licks on our farm over a period of 3 years.The deer,or any other animal for that matter hardly touch them.
Our farm borders a salt water marsh,tidal river and Delaware Bay = Lots of available salt.The conclusion we've come to,is they have ample salt in their diet.We stopped puttin them out.We've had tons of luck with blocks containing various seed product,
molasses,and apple resin - they tear that up - gone in couple weeks!!