Edit: I used to dismiss all that since I figured animals don't have enough neurons or intelligence or whatever for their pain to matter. A quote from Ozy Brennan[1] (five paragraphs down from this hyperlink, though BB's commentary here is important too) changed my mind. TL;DR: intelligence is almost certainly not relevant to feeling pain, and the same pain pathways that exist in the human brain exist in other animals too.
[1] https://benthams.substack.com/i/151605056/2-intensely-what-a...