Essential amino acids

Essential amino acids are the amino acids an animal cannot make in sufficient quantity itself and must therefore receive ready-made from its food. Of the roughly twenty amino acids that build proteins, about half fall into this category, and the exact list depends on the species. This is where dogs and cats part company: the cat, an obligate carnivore, needs [taurine](/glossary/taurine) as a dietary essential, whereas dogs can usually synthesise enough of their own. Cats also have a higher requirement for [arginine](/glossary/arginine) and cannot make [methionine](/glossary/methionine)-derived nutrients as flexibly. A protein is judged not only by its [crude protein](/glossary/crude-protein) figure but by whether it delivers every essential amino acid in the right proportion: the one in shortest supply, the limiting amino acid, caps how well the whole protein can be used. On a label, essential amino acids rarely appear by name, though you may see added [lysine](/glossary/lysine), DL-methionine or taurine listed among the additives. A striking illustration of why these nutrients matter: taurine deficiency in cats was identified in the late 1980s as a cause of a reversible heart muscle disease, dilated cardiomyopathy, and correcting the diet reversed the damage (NRC, 2006). Deficiency signs vary by amino acid but commonly include poor growth, dull coat and, in cats, cardiac and retinal problems. A complete commercial food is formulated to cover every essential amino acid for the relevant life stage.

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