I've done some reading on sodium nitrite. The problem is getting them to eat it as it tastes and smells bad. Once they get a small dose, they avoid it. Researchers have been trying to find a way to hide it in some kind of edible feed. One article I read said that they've had good luck with gummy bears.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.