I don't have much milkweed growing where deer can reach it, just some swamp milkweed that they haven't eaten...knock on wood!
I don't get the impression that the "milk" in milkweed is nearly as poisonous as we've been told. Monarchs get eaten by predators just as much as other cats - the only caterpillars I know of that are really distasteful to predators are pipevine swallowtails, and there is a big predatory stink bug that will even eat them when it shows up.
Plus, deer are known to eat most anything!
Sherry

I live in so. ca. in a townhome so no deer, overnight something bit all the stems of my butterfly weed clean through, on a diagonal. As if you took a sharp knife and cut at an angle for a floral bouquet. Cannot find it anywhere on google, Bought a new one, 24 hours later, same thing, They touch nothing else>

The deer do sample the milkweed here. They especially like the flowering tops or just the young tender leaves..