Lover Horse Head

I can't remember the name of it for the life of me. I haven't seen the movie in a while, all I remember about it, is that it was REALLY trippy. Something about getting stuck inside some killer's head and something about a little boy being abused? I do remember one scene very vividly though. The actress walks into a room and sees a horse standing in the middle, then a huge slicer thing comes down and slices the horse into about 20 pieces. (the only realy I remember that is because I am a horse lover and that really disturbed me) If someone could help me figure this out I would be very greatful! Thanks!