I remember reading about some guy about 15 years ago that became so “vegan” that he even made his cat a vegan. The cat went blind.
My BIL did that to his dog only he was just vegetarian. The dog had non stop diarrhea and gas until he gave him decent dog food.
Vegetarians and vegans IMO are a form of anorexia.
Cats are “Obligate Carnivores”...meaning they must have an all-meat diet or a majority-meat diet to grow and stay healthy.
All the crap that pet food manufacturers put in (grains, veggies, etc.) are just fillers or to make the food visually appealing...to humans.