If a life form alien to me was going to suddenly, randomly (from my perspective) kill me to use me as food, I don't think I would necessarily mind because I had no idea it was going to happen. If I lived my entire life in fear that I could be killed at any moment, I'd be less ok with it.

I guess what I was going for was that trying to compare a chicken's understanding of mortality to our own isn't a compelling argument to me. I think the simple fact that they're alive and deserve to be treated with dignity is a better argument.