Animal vs plant protein

The animal versus plant protein distinction classifies proteins by their origin, and it matters chiefly because of amino-acid profile and how well dogs and cats can use each. Animal proteins, from meat, fish, egg and organs, generally supply the full set of [essential amino acids](/glossary/essential-amino-acids) in proportions close to what these species need, and they tend to be highly [digestible](/glossary/digestibility). Plant proteins, from legumes, cereals and oilseeds, can be perfectly good protein but are more often short of one or more key amino acids, frequently [methionine](/glossary/methionine), [lysine](/glossary/lysine) or [taurine](/glossary/taurine), and they carry anti-nutritional factors such as phytates that can reduce mineral availability. The species difference is decisive for cats: as obligate carnivores they have an absolute, preformed requirement for taurine and arachidonic acid that plants simply do not provide, so a plant-only diet is far harder to balance for a cat than for a dog, and risky without expert formulation. None of this makes plant protein inherently bad or animal protein automatically superior; what counts is the final amino-acid balance of the complete diet, and a well-designed recipe can blend both. Quality also varies enormously within each category, so the source name on the label matters as much as whether it is animal or plant. See the [Petipedia glossary](/glossary).

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