They're going to go into winter in real good shape, with a lot of fat. Those fat reserves, they're going to use them in the winter. The more they have, the better off they are. They can be. Deer should be hanging right in there, pigging out.
Deer eat all sorts of things.
The lists I've seen of preferred deer food are long and varied. They include crops like corn and alfalfa, plus white cedar, birch, aspen, mountain ash, witchhobble and much else. I've seen them strip the fuzzy red fruit of staghorn sumac as high up on the bushes as they could reach, and gobble up oak leaves even when there was seemingly more nutritious food readily available. Check out those nutty areas. You won't regret it.