After a buck loses it's antlers, it doesn't take long to begin his new growth of horns.  Usually by April you can see horns beginning to re-grow.  I always laugh at the bucks around our house during the time they are without horns.  The larger animals seem to not quite understand what has happened and their ears seem to hang really low like they are afraid to perk them up. They almost look embarrassed!  The more minerals and nutrition they receive nutritionally during early spring and summer, the better the horn re-growth is.