Horses killed in this film?

If you watch closely, it seems that at least some of the race footage was either from actual races where jockeys fell and not stunts done for the film, or the editing was just not perfectly done. The horse which was lying on the ground was pretending to be hurt. You see the man holding the gun to shoot it and hear the shot, but don't actually see the horse shot, not only because that would be gross on camera, but because the horse was not actually hurt and the sound of even a blank shot would have startled it.