Yes I have had deer twitch on several occasions . came up behind one one time and poked it with my muzzle and got no reaction and then went to spread its legs to start the gutting process and they started twitching and flailing like crazy. Mind you this was probably witchin mins of coming down from my stand and walking over to the deer.

Here is a video of a deer twitching sometime after it was killed.

No one cares about the big horn sheep. God I love this video.