Anonymousblood sacrifices would practiced by the Druids, but not as a sacrifice itself, in celtic times animals were kept for food and this meant that when winter approached , non breeding or milk stock would be slaughtered. being a so close to the natural world and knowing that all things were given by the gods , animals would be slaughtered with reverence and gratitude and this would be done by the villiage holy man, they being the closest to the gods and best able to pass the appreciation on. It is also quite possible that at certain times of great stress , Druids themselves could have been sacrificed. (lindow Man).