The singer, 36, announced her plant-based plans on Saturday night, sparking fierce debate among her 109 million Twitter followers.
The popstar, who is engaged to British actor Orlando Bloom, tweeted: "I'm about 95% ready to be 100% VEGAN... my dog Nugget has been joining me on this journey for the past 4 monthz.
"Pray for us ok."
The declaration proved instantly divisive, as critics branded the move cruel to animals, while supporters defended Perry’s choice.
One user tweeted: "I hope Nugget has only been joining you for emotional support!
I’m about 95% ready to be 100% VEGAN... my dog Nugget has been joining me on this journey for the past 4 monthz. Pray for us ok ✌🏻♥️
— KATY PERRY (@katyperry) January 16, 2021
“Dogs shouldn't be vegan, so please continue providing their necessary requirements! Also I mean being imperfectly vegan is fine like just do your best out there and don't beat yourself up for any mistakes."
Another commented: "Dogs can't go vegan they're carnivore," alongside a sad face emoji.
But another insisted that dogs could, safely, follow herbivorous diet, writing: “Please stop spreading misinformation.
“Dogs absolutely can thrive and vastly improve their health on plant based diets. I urge people not to read silly comments like this and please do actually research on the topic."
Meanwhile, another user suggested Perry was, indeed, referring to the emotional support offered by her pet during her lifestyle transition, and not to Nugget’s own dietary requirements.
They tweeted: “Now that I've seen a couple of tweets about this, I think she might be referring to Nugget (her dog) joining in but emotionally, like, Katy feels that her dog has been supporting her throughout the process.”
Perry has not yet clarified what she meant.
Experts have suggested that while cats must follow a meat-based diet, it is possible for dogs to be vegetarian.
However, the president of the British Veterinary Association (BVA) previously told the BBC that this is "much easier to get wrong than to get right.”
Daniella Dos Santos explained to the news site last year: "In the UK, under the Animal Welfare Act the owner has the obligation to feed the animal an appropriate diet.
“If your personal belief system means you don't want to eat any animal protein, that's fine, but that diet is not designed to meet the welfare standards of your pet.
Ms Dos Santos continued: "It is theoretically possible to feed a dog a vegetarian diet, but it's much easier to get it wrong than to get it right.
"You would have to do it under the supervision of a veterinary-trained nutritionist."