interesting. I had a kurdish muslim neighbour several years ago, and he introduced me to this practice which I wasn't previously aware of. what I found interesting about it is that they'll often slaughter the animal over a ditch or hole dug into the ground into which the blood is drained, which is the process for making offerings to chthonian (ie. underworld) deities in most pagan traditions. they probably don't realize that, but it's almost certainly where the tradition originated. apart from the practical benefit of that method being ergonomic and less messy.