obligate carnivores

All felids, including domestic cats, are obligate carnivores. But, the cat is not alone in being a strict meat-eater. Other mammals that are classed as obligate carnivores include mink, tarsiers, dolphins, seals, sea lions and walruses, to name a few.² Non-mammal obligate carnivores include rainbow trout, salmon, hawks, eagles, crocodilians, many snakes and lizards and most amphibians.³

 

All of these animals became obligate carnivores as a result of their ancestral diets. Because eating a meat-only diet provides some vitamins and fatty acids in their pre-formed state, cats and many other obligate carnivores have lost the ability to make these amino acids and vitamins in their own bodies the way herbivores or omnivores do. They don't need to since the animals they are eating have already done it for them. For example, cats require vitamin A in its pre-formed state, they can't make it from beta-carotene the way humans or dogs or rabbits can. They have little ability to form niacin from tryptophan.⁴ They have a high requirement for taurine, which is found almost exclusively in animal flesh.⁵ Arginine, also found in animal flesh, is so critical to the cat that a meal without it can lead to death.⁶ Fortunately, all meat sources have plenty. Simply put, cats must eat meat to live.