A lot of vegans will hate this, but YOU'RE NOT A FUCKING SCIENTIST! Drop all the journals and research you want, but your pet is not a lab-controlled experiment. Besides, something being in a journal doesn't make it true. If it is regularly cited as true, and has swept into general understanding of how to feed a pet, then it's factual...

I'm all for vegans living their best lives. Don't force it on a pet that doesn't know better. Vegans harming animals through their own food choices isn't a new thing, ask most vets and they'll have seen the effects of malnutrition from someone that thought that they knew better.