Idiosyncrasies of amino acid metabolism in dogs and cats

Abstract Text:

Both the dog and cat have been domesticated for thousands of years yet they retain some unique metabolic nuances.  While both are classified as members of the order carnivora they each have nutritional and metabolic requirements that differ from the majority of domestic species.  The dog is considered a nutritional omnivore adapting to a wide range of foods and nutrient sources, whereas the cat is a strict carnivore showing little nutritional or metabolic adaptation with changes in diet.  The cat has little ability to adapt amino acid degrading enzymes to dietary protein restriction and conservation of protein and shows little change in urea cycle activity with changes in diet.  This contrasting adaptability leads to differences in the nutrient profiles required by each.  In addition to requiring greater quantities of dietary protein, the cat requires a dietary source of taurine because of its obligate use of taurine for bile acid conjugation and a limited ability to synthesize taurine from sulfur amino acids.  Although taurine is not strictly required in the diet of dogs, it has been suggested that taurine may be required in the diets of certain large breed dogs.  Like cats, dogs also use taurine for bile acid conjugation but they have a greater taurine synthetic ability and can adapt for use of glycine for bile acid conjugation.  Both the dog and cat require a dietary source of arginine with the cat being extremely sensitive to its absence.  This occurs as a result of the limited ability of cats to endogenously synthesize ornithine and citruilline to maintain urea cycle activity because of low intestinal enzyme activities compared with omnivores.  The cat also has a limited ability to use tryptophan to synthesize niacin.  Again this occurs from evolutionary adaptations in enzyme levels.  Additional nuances include higher requirements for sulfur amino acids in the cat because of needs for hair and felinine synthesis.  Overall, the cat appears somewhat unique but metabolically and nutritionally it appears similar to other strict carnivores.

Keywords:

Feline, companion animal