If deer are feeding in a fescue field, as Popcorn pointed out, they are not eating the fescue (except by accident). They are eating the wild clovers/legumes and broadleaf weeds growing in the fescue. Deer do not have the gut bacteria necessary to digest grasses.
And as Popcorn suggested: rye, wheat, oats, annual clovers, brassicas will all do well in little "shooter" plots.