I am training my Lab pup to track and blood trail, and I saved some blood from the deer that I have killed this season for off season practice. According to some resources that I have used, one ounce of blood is supposed to do a 200 yard trail, so it doesn't take much.

My pup has "found" 3 deer for me so far. Here is a picture after her best trail yet. It was a 200+ yard trail, and she had to cross a creek on the trail.