You could try a salt lick, or just make your own.
1 part dicalcium phosphate
2 parts trace mineral salt
1 part stock salt
Then mix in some dry molasses or high protein liquid feed. You can buy the stuff in large quantities and store it in a big Rubbermaid tub. They will literally dig a hole in the ground trying to get the last of it. Just make sure you put it on bare ground or really short grass.
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Question on these spypoints. Are the pictures sent to your phone, or is it possible to setup them up to send directly to a computer or file folder? I'm new to the wireless ones, but would like to try them. My cameras usually average 1,000 - 2,000 pictures every two weeks, so I'd hate to have to manage that many pictures using my phone.