Buffington also said that it's easier for dogs to adopt a vegan or less-restrictive vegetarian diet because their nutritional needs aren't as strict as those of cats.
Animal welfare advocates share his concerns.
"With humans, of course, we believe that whether or not to consume meat is a personal and private choice. With our pets, of course, we're deciding for them," said Mindy Bough, senior director for the American Society for the Prevention of Cruelty to Animals. "Someone has to look at their own personal views and work with a veterinarian to make sure nutritional deficiencies aren't occurring."
Dogs, she said, are mostly carnivores, but because their diets are more varied, they could get away with a vegetarian diet that also includes eggs and other meat products. Vegetarian diets can include eggs, milk and other animal products, whereas vegan diets cannot.
Although there are commercial vegan diets available, Bough said, "I am personally reluctant to recommend that as a first choice."
Cats, however, are another matter entirely, she said.
As obligate carnivores, cats have stringent dietary requirements and it's more challenging to make sure they get the nutrients they need, including the amino acid taurine, vitamin A, iron, calcium and vitamin B.
Although she's heard anecdotally of healthy vegan cats, she said she suspects that those cats may be supplementing their meat-free diets on their own.
"If they're not getting meat, they're probably going to try to hunt -- maybe for the mouse in the house or the bird in the yard," she said.
But pet owners like Moore and the manufacturers of vegan pet food maintain that most veterinarians don't have enough training in nutrition.
"Here's the reality: We've been doing this for 20 years. We have dogs over 19 years old in good health. We have cats over 22 years in good health," said Eric Weisman, CEO of Evolution Diet Pet Food Corp., a manufacturer of vegan cat and dog food.
Weisman said thousands of clients across the United States, including animal shelters, use his vegan pet foods with success.
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