That burden of proof doesn't fall on me. I was rebutting your claims that relied on nature and on mechanisms, and explained why the reasoning doesn't hold up. The reason I asked for a study is because if you can't produce an argument on why we couldn't feed animals in a vegan manner then a study that showed poor health outcomes would at least require me to explain how those specific hurdles are solvable.

I completely agree with you that I shouldn't have a cat because I have not done the research on how to feed a cat in a vegan manner, but that's something most people have not done because they simply don't care about feeding a cat in a vegan manner. In my view they should not have cats either.

As for meat grown in a lab, I am fine with it. But ethics aside ultimately I think we shouldn't evaluate food on how natural it is but how provably healthy it is. If we can formulate food that gives cats better health outcomes then we should be feeding them more of that. This is anecdotal, but of the dogs I know through family or friends the ones fed way more plain meat have the worst digestion and I wouldn't be surprised if they died the earliest, but it's hard to talk people out of these naturalistic positions.