a mass slaughter of all other pigs
Isn't this what's happening all the time anyway?
Not in the sense I was using it above, namely, "We kill them all at once to remove their population." What's happening at present is more like "we kill them in batches to meet production demands, and bring in more." Aggregated over the very long term a whole lot more pigs can suffer and die in the second case; I'm simply saying I don't find "One sudden, nearly-complete mass slaughter" to be a preferable alternative.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.