Dream meaning, heard of horses trying to kill me?

I keep having a dream where a heard of about 30 horses are chasing after me, very angrily, trying to kill or hurt me. The cirstances and people i am with are always different, but in each dream a large heard of horses, who are unprovoked by me or the people i am with, seem to strain to get to me in anger, in one dream they collectively bashed themselves against a gl window until they smashed it and got to me, and then chase after me as i run in terror. Does anybody have any idea what this could mean? Thanks :) xxx