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Elk love salt
I have had elk coming in almost daily to trace mineral salt with selenium. It is about $9 for a 50 lb bag.
They walk miles for garbanzo beans (chickpeas). A mix of barley, canola meal and northwest beef mineral from Wolfkill Feed (about $12 for 50 pounds) might be the very best. You might add some limestone for calcium if you feed any quantity. Try 10# barley, 2# canola meal, .5# northwest beef and .5# limestone. The mineral all by itself will make elk excavate large holes to get all of the stuff.