I think you can figure about 6-8 weeks. I' m going by the fact that goats will not let the young nurse after 8 weeks. And I fugure that goats may be one of the closer animals to deer. The four to six week period may be when the doe will start to get them to start grazing.
Dan, most of the posts have the opinion that deer won' t touch Rape until a frost. I planted some Rape around the edge of my newest Clover plot, checked today and it is all gone, 1 inch stubs. It was 8-10 inches tall. Got a strip 100 feet by 5 feet along my South fenceline. Put it in later, but I better check it out.
Russ