Arginine

Arginine is an essential amino acid for both dogs and cats, but it carries an outsized importance in the cat. Its central job is to keep the urea cycle running, the liver pathway that converts toxic ammonia, released when protein is broken down, into urea for the kidneys to excrete. Cats synthesise very little arginine of their own and have a high requirement, because their urea cycle never idles: it stays active even during fasting or on a low-protein diet, a direct consequence of obligate-carnivore metabolism. The result is one of the most dramatic deficiencies in nutrition. A single arginine-free meal can drive ammonia to dangerous levels within hours, producing vomiting, drooling, neurological signs, muscle spasms and, untreated, death (NRC, 2006). This is precisely why a complete cat food always carries enough arginine, and why an unbalanced home-prepared ration can be genuinely hazardous for a cat. The richest sources are animal proteins such as meat and fish, so a meat-based diet rarely falls short; the danger lies in poorly formulated or purified diets. As one of the [essential amino acids](/glossary/essential-amino-acids), arginine sits alongside [taurine](/glossary/taurine) and [methionine](/glossary/methionine) among the nutrients that make feline diets distinct. See the [Petipedia glossary](/glossary) for related entries.

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