One thing you will learn to pick up on if you do your own meat is the distinct smell of an animal starting to turn bad. As you walk into the room take a big sniff. You will detect a seemingly sweet smell, not that musty smell you had the day after you hung it, especially around the neck area. It always seems to go first. Even at this stage you can cut the affected area away until you notice the smell goes as well. I don't recall having this with a deer but I have with a moose. I've eaten it and I'm still here.