Yes, lots of people already brought up warm water but absolutely. The only issue there is if your horses feet are extremely sensitive. One of my Thouroughbreds is very sensitive and if his feet get even a little wet, he's lame. If you can bring your horses indoors, I would start there. Then if their feet aren't too sensitive, use the warm bucket of water. If the feet are sensitive, I would keep them inside in an area with little-no concrete, to avoid falls and let the ice loosen up before going at it again.