I don't want to hijack the thread, but was just going to post something similar after few results came up in google.
My horse doesn't have the option to go in during the day if she wants (she is in her stall at night). The BOs pen she is in was pure mud / crap, etc. which froze. She now has hooves that looked "blushed" in places which I know means that they are slightly bruised. I'm going to guess that this was caused by the ground being uneven so hard (thanks to the arctic blast).
I'm hoping it doesn't turn into anything serious. Of course I'll be keeping an eye on them daily.
Has eveyone else had bruises from frozen uneven ground? If so, did it turn into anything serious or go away in a week or so with no harm done?