I have heard a lot of people say that you can taste stress in the meat of any species and especially pig.
I absolutely believe it to be true; certainly we believe that some of the excellent tenderness and flavour in our own meat (lamb, mutton, beef and pork) derives from the as-stressfree-as-possible last 24 hours. We use a local small abattoir, take the animals ourselves in our own trailer, normally they are slaughtered within minutes of arrival, the handlers at the abattoir are great and you never see any harsh handling or signs of stress (in handlers or animals!)
However I know that I want it to be true, so I could be self-deluding. And our pig ended up not being slaughtered till the next day as they had an equipment failure the day we took her in - and the meat tasted fantastic. (But they would have looked after her well and so even though she'd have been in a strange place for 24 hours she maybe would not have been too stressed by it.)