It's simply a SALT block. Deer do prefer salt in their diet to help them digest but it certainly isn't a magic pill that's gonna have them crossing rivers to get to. Also, it needs planty of rain on it to give it a chance to dissolve into the ground. My guess is that next season, assuming it's located in a decent deer area, the animals will start to paw and eat the dirt at that location.
The results should look something like this "hole" on a friends farm in SE IA. This spot was created by simply putting a couple of Apple flavored salt blocks from Evolved Habitats at the loaction the season before. Good luck
