What matters is the amount of empathy we feel with the creature. With dogs, we often think of them as our friends and companions. With mice, we often think of them as vermin and a problem.
Though, I'm sure if you took George's mouse Milo and fed it to a snake George would be extremely upset.
That's pretty far outside the mainstream -- lots of jurisdictions have laws about the humane slaughter of animals.
For obvious reasons, people tend not to restrict their moral consideration of pain to those beings that will never die.
The vast majority of people don't care at all. But the people who do care care a lot, and make a lot of racket.
> For obvious reasons, people tend not to restrict their moral consideration of pain to those beings that will never die.
I honestly have no idea what you could possibly be talking about. Can you rephrase? Specifically, since the set of "those beings that will never die" has size zero, the sentence seems like a truism.
If I understand this correctly, you were saying that the animals' deaths essentially render their suffering irrelevant. It seems to logically follow that if everything is dead "at the end of the process" then there's no suffering that we need ever care about.
I don't honestly think you hold that position, but it's at least consistent with your earlier post, so it'd be nice to know where your logic breaks from mine.