Why would the pig know if was going to die? I've seen pigs butchered on a farm. The butcher just shot then once in the forehead with a .22. Instant lights out.
Related... the silence of the lambs thing I witnessed first hand. A bunch of sheep taken off to be slaughtered, standing in complete silence. Welsh sheep are never silent, so it spooked me a lot. No visual cues as to their impending doom, yet they all stood there like ghosts.
This doesn't mean that any pig could articulate "I'm going to die". That isn't necessary. Nearly every ungulate (maybe not moose?) has a built-in mortal fear ready to surface at any time. New events, or repeated events with bad associations, bring out that fear. It takes a great deal of training to relax that.