Have you tried emailing the companies about the foods you're interested in, Yamcha? If you ask them directly if they use euthanized cats and dogs or if they use 4-D meat, you should get a straight yes or no answer. If they hedge, dodge, or otherwise divert from the question, it would certainly make me very suspicious about the protein sources they use...
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."