I don't think that blood and gut piles have a negative effect on deer at all. As a matter of fact, I think it can help you at times. I had a doe with 2 fawns come in one night, and while they were walking away, they hit the blood trail from a doe I had shot 4 days earlier. This just made them curious, and they followed the trail for about 30 yadrs, then turned around and followed it right back to my stand. I wasn't going to shoot any of them, but if I had wanted to, the blood actually brought themback in and gave me another opportunity.