Alfalfa. Grass has no benefit- except they may bed on it.
Corn is just fine as long as there’s corn in the area they have been eating. They simply need the bacteria in their stomachs for digestion of corn. If u got picked corn around - u are just fine!!! The only folks that’s really an issue…. Say u in a forested area. Or in some big pasture area…. Deer stressed & hungry & been living on low quality sparse natural browse…. U throw out a corn pile- can kill em. Corn growing areas- no problem.
If folks want “free food for deer” & “free excercise”…. & the best food… go find hickory stands where the trees are growing about 10x thicker than they should be. Dump the clusters over with a chain saw leaving the best poles (crop tree release). Or elms. Or any “poor quality tree” competing with great trees. Those fresh buds on the ground - loaded with digestible premium nutrition!!!