Interesting side effect. I embarked on an evil biome for ‼SCIENCE‼, and immediately slaughtered my pack animals on the evil biome. This one is a bit more forgiving; there was a decent delay before they all rose; I drafted everyone and the hair, which rose first, was easily beaten to "death". The donkey skin died likewise after a scuffle, and lastly the horse skin was hacked, causing another piece to fly off and animate. Both the skin and the left leg skin or whatever it was were killed. For some strange reason, they never rose again; I waited twice as long and it was for nothing, none of the three rose. Not sure if there's something about that, but I'm planning to re-embark and deliberately slaughter and kill something just to see if the skins and hair stay dead once put down, or if they are just amazingly delayed or what. Also, planning to pit a cat or something off a cliff so it dies without being broken into meat and skin and such, and see if the effects are different on a corpse instead of skin.
Anyway, the interesting side effect is that the horse skin produced a leather when tanned, as normal. Strangely, the horse skin left leg or whatever I hacked off it ALSO was tanned into a normal piece of horse leather. So, free horse leather.