I have shot many caribou and have found the big bulls are fine by end of Oct. Our rut here for barren ground is peak around the 15 Oct, the younger bulls tend to go on for a bit longer, but the bigs bulls have broken away from the cows and are fine to eat by the end of the month. If you watch then for a bit you can tell if the bulls are still playing around or have completely abandoned the cows. It seems it doesn't take long for the rut to clear their system after they quit, 2 or 3 days seem to do it from inedible to good. These are Yukon caribou and I've never seen or hunted the NFLD ones so take my experience for what it's worth.