Mine are stalled in 12x12 stalls that are matted with at least 6 - 12 inches of shavings (I'm a shavings aholic!) AND I have a TWH mare that always has them... Also my mare asia is a PITA with them. I bed super deep... I think she egts them from laying down outside. Its rocky and hard and thats about the only way I can think of that she'd tear her self up like that.