“Amino Acids in the Nutrition, Metabolism, and Health of Domestic Cats”, 2019 ():
Domestic cats (carnivores) require high amounts of dietary amino acids (AAs) for normal growth, development, and reproduction. Amino acids had been traditionally categorized as nutritionally essential (EAAs) or nonessential (NEAAs), depending on whether they are synthesized de novo in the body. This review will focus on AA nutrition and metabolism in cats.
Like other mammals, cats do not synthesize the carbon skeletons of 12 proteinogenic AAs: Arg, Cys, His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Tyr, and Val. Like other feline carnivores but unlike many mammals, cats do not synthesize citrulline and have a very limited ability to produce taurine from Cys. Except for Leu and Lys that are strictly ketogenic AAs, most EAAs are both glucogenic and ketogenic AAs. All the EAAs (including taurine) must be provided in diets for cats. These animals are sensitive to dietary deficiencies of Arg and taurine, which rapidly result in life-threatening hyperammonemia and retinal damage, respectively.
Although the National Research Council (NCR) (Nutrient requirements of dogs and cats. National Academies Press, Washington, DC, 2006) does not recommend dietary requirements of cats for NEAAs, much attention should be directed to this critical issue of nutrition. Cats can synthesize de novo 8 proteinogenic AAs: Ala, Asn, Asp, Gln, Glu, Gly, Pro, and Ser, as well as some nonproteinogenic AAs, such as γ-aminobutyrate, ornithine, and β-alanine with important physiological functions. Some of these AAs (egGln, Glu, Pro, and Gly) are crucial for intestinal integrity and health.
Except for Gln, AAs in the arterial blood of cats may not be available to the mucosa of the small intestine. Plant-source foodstuffs lack taurine and generally contain inadequate Met and Cys, and, therefore, should not be fed to cats in any age group. Besides meat, animal-source foodstuffs (including ruminant meat & bone meal, poultry by-product meal, porcine mucosal protein, and chicken visceral digest) are good sources of proteinogenic AAs and taurine for cats.
Meeting dietary requirements for both EAAs and NEAAs in proper amounts and balances is crucial for improving the health, wellbeing, longevity, and reproduction of cats.
…In contrast to most species of dogs, cats have a very limited ability to produce taurine from Cys because of a low activity of cysteine dioxygenase and cysteinesulfinate decarboxylase, and therefore taurine must be included in the feline diets (Case et al 201113ya; Knopf et al 197846ya; 1992). Clinical syndromes of taurine deficiency in cats include retinal degeneration, poor reproductive performance, fetal and post-natal developmental abnormalities, and dilated cardiomyopathy ( et al 2018; Hand et al 201014ya; 1995). The recommended intake of cats for dietary taurine is 0.2% (NRC 2006), which is below taurine content in meat (0.23% to 0.29%) ( et al 2016).