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Arginine in dog and cat diets

A short guide to the role of Arginine in dog and cat nutrition.

Arginine

An exogenous (strictly essential) amino acid for dogs and cats. Besides building proteins, its key task is to drive the urea cycle in the liver. Digesting large amounts of meat releases toxic ammonia, and thanks to arginine it is instantly converted into safe urea and excreted in the urine [1]. Arginine is also a substrate for the production of nitric oxide (regulation of blood pressure and vessels), supports wound healing and immunity.

Species difference: A dog has a limited but non-zero ability to produce arginine from citrulline — this gives it some margin. A cat practically does not synthesise arginine at all (negligible activity of intestinal enzymes) and is completely dependent on the diet. In experiments, a single meal devoid of arginine caused severe hyperammonaemia in a cat within a few hours [2]. This is why the NRC standard for a cat is more than twice as high (RA ≈ 1.93 g/1000 kcal) as for a dog (RA ≈ 0.88 g/1000 kcal) [1].

Where it's found: Practically every animal-derived protein — muscle meat (breasts, thighs, beef, venison, horse meat), hearts (amino-acid-wise like muscle meat), fish, offal and eggs. It does not require supplementation in a meat-based diet. Gelatin and collagen tissues (skin, tendons, ears, hooves), on the other hand, are poor in arginine — this is an important source of problems in the calculator.

Deficiency: With a serious deficiency, ammonia builds up in the blood — profuse drooling, vomiting, an unsteady gait, tremors, severe neurological seizures, and in extreme cases coma and death [2]. But on a raw meat diet this is a scenario bordering on impossible, because there is plenty of arginine in meat. Low arginine in the calculator does not mean you need to buy a supplement — it is a signal that the whole recipe has too much collagen (gelatin, skins, tendons, excess bone) at the expense of real muscle meat (see Protein). Neurological symptoms after a meal on a meat-based diet are above all a signal for an urgent visit to the vet (liver disease, a congenital vascular defect), not for changing the recipe.

Excess: From food it is not a problem — a healthy animal's body efficiently metabolises and excretes the surplus. The only real risk is supplementation with pure arginine in large doses: it can cause diarrhoea and impair the absorption of lysine and other amino acids that share the same intestinal transporter [3]. Therefore do not supplement arginine "just to be safe" or "for sport".

What to do when the calculator shows low arginine

Check the proportions: how much of the diet is muscle meat, how much is collagen components and bone. Increase the share of lean muscle meat and hearts, reduce collagen tissues and excess bone, recalculate. In cats, watch out for diets based mainly on eggs (rich in methionine, but poorer in arginine) — look at both parameters together.

Sources

  1. National Research Council (NRC) (2006). Nutrient Requirements of Dogs and Cats. National Academies Press. Arginine: dog RA = 0.88 g/1000 kcal ME, cat RA = 1.93 g/1000 kcal ME. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. Morris JG, Rogers QR (1978). Ammonia intoxication in the near-adult cat as a result of a dietary deficiency of arginine. Science 199(4327):431-432. https://doi.org/10.1126/science.619464
  3. Li P, Wu G (2023). Amino acid nutrition and metabolism in domestic cats and dogs. J Anim Sci Biotechnol 14:19. https://doi.org/10.1186/s40104-022-00827-8
  4. Merck Veterinary Manual (2024). Nutritional Requirements of Small Animals. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals