> They have nervous system, therefore they feel pain, just like us.

That's two non-sequiturs in one sentence. I'm pretty sure there exist lifeforms that have a nervous system without an analog of pain. (Hint: If you want to defend your argument, start by defining "pain".) And it's quite egregious to just assume that there exist only one kind and quality of pain in all living animals. (Again, start by asking yourself how to rigorously define "pain".)

> They also suffer emotional pain, not just physical. Kill a pig in front of another pig and he/she is going to be terrified.

If at all, that's just an argument not to kill pigs in front of other pigs (unless the emotional pain is a desired outcome).