This technical letter, published in a leading UK veterinary journal, summarised the evidence extant by May 2022, about health outcomes of dogs on vegan vs meat-based diets. Four studies showed equivalent or superior health outcomes for dogs on vegan diets (compared to meat-based dog food), and one study (the oldest, smallest) showed a contrary result.
Knight A (2022). The weight-of-evidence position on vegan diets. Vet Times 52(21), 23.