If you just want to keep them interested you can mix in some molasses with the corn and throw it out and pour some on an old stump, you can also just mix some C'mere deer with the corn also. Here is a recipe for a homemade mineral lick that has worked for me.
1 part Di-calcium phosphate, this is a dairy feed additive bought at feed stores.
Comes in 50lb Bags at around $11.00 you need one bag.
2 parts Trace mineral salt, the red and loos kind without the medications.
Comes in 50lb Bags at around $5.00 you need two bags.
1 part Stock salt, ice cream salt.
Comes in 50lb Bags at around $2.00 you need one bag.
Directions:
-Use a 3 pound or similar size coffee can to use as your measure for each part of the mix.
-Mix all together well but not until read to use, keep ingredients separate until ready to put to use.
-Dig or tear up a circle in the soil about 36 inches wide and about 6 inches deep.
-Mix your mineral mixture with the soil.
Maintenance:
-Replenish in 6 months with fresh supply of mineral, and then each year there after.