To date, about 450 dog breeds and 60 cat breeds with differences in shape, size, and color are recognized globally. The feline domestication occurred approximately 10,000 years ago. The cat, which was also from the order Carnivora, is the only domesticated species in the family Felidae. The dog is a domesticated descendant of the grey wolf (an obligate carnivore), and was from the taxonomical order Carnivora over 15,000 years ago. The compound annual growth rate of the global petfood market is expected to be 4.6% between 20 (monetary value, US $124.9 billion by 2027). Thus, the global petfood industry has grown substantially in recent years. Most petfoods are commercially manufactured, although some people choose to prepare meals for their own pets by using animal- and plant-sourced ingredients. In the United States, 25.4% and 38.4% of households owned cats and dogs, respectively, in 2018, as companions or family members. For example, the numbers of domestic cats and dogs in China have increased gradually between 20 by 677% and 147%, respectively.
These animals contribute to the mental health and well-being of children, adolescents, and adults, and have become increasingly popular in many countries and worldwide over the past decades (Table 1). The domestic dog ( Canis familiaris) and the domestic cat ( Felis catus) have been human companions for at least 12,0 years, respectively. Pet-food grade animal-sourced foodstuffs are excellent sources of both proteinogenic amino acids and taurine for cats and dogs, and can help to optimize their growth, development, and health. Adequate intakes of high-quality protein (i.e., 32% and 40% animal protein in diets of aging dogs and cats, respectively dry matter basis) are recommended to alleviate aging-associated reductions in the mass and function of skeletal muscles and bones. Throughout adulthood, cats and dogs may lose 34% and 21% of their lean body mass, respectively. Compared with dogs, cats have greater endogenous nitrogen losses and higher dietary requirements for many amino acids (e.g., arginine, taurine, cysteine, and tyrosine), and are less sensitive to amino acid imbalances and antagonisms. Thus, concentrations of both taurine and arginine in feline milk are the greatest among domestic mammals. De novo synthesis of arginine and taurine is very limited in cats. Certain breeds of dogs (e.g., golden retrievers) are more prone to taurine deficiency possibly due to lower hepatic activities of cysteine dioxygenase and cysteine sulfinate decarboxylase. Although most breeds of dogs have potential for adequately converting cysteine into taurine in the liver, a small proportion (1.3%–2.5%) of the Newfoundland dogs fed commercially available balanced diets exhibit a deficiency of taurine possibly due to gene mutations. Dogs inadequately synthesize citrulline (the precursor of arginine) from glutamine, glutamate, and proline in the small intestine. This article highlights both proteinogenic and nonproteinogenic amino acids. Domestic cats and dogs are carnivores that have evolved differentially in the nutrition and metabolism of amino acids.
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