We never had this problem until our son brought in a new horse about 6 months ago. When they're out in the field, he chases the other 3 horses or he'll walk up to one eating grass and start nipping at their necks. There Re no bite marks but plenty of hoof scratches where the hair and top layer of skin is shaved off.
My Buckskin is non aggressive and gets chased the most. His back leg has bad scrape all the way to his hoof and is swollen.
This hose is now picking on our DRaft that out weighs him by about 1000 lbs. The Draft has had him on the ground already but the horse won't stop. We're afraid the Draft is going to kill him.
Do your horses "play" like this? I really don't think they're playing but don't know much about this. I just know that the horses weren't cut up until this new one came into the herd.
My son says they're just playing.