One of the methods I use to train a pup to discriminate is by laying the training track late in the afternoon on the edge of a field that you know deer will visit during the night. In the morning if the pup tries to follow a healthy/hot track into the woods or out into the field, then just give it a firm correction. It won't take long for it to get the message. A dog that messes with healthy deer can never make a serious tracker.