Characteristics of Nutrition and Metabolism in Dogs and Cats

Domestic dogsDog and catsCat have evolved differentially in some aspects of nutritionNutrition, metabolismMetabolism, chemical sensing, and feedingFeeding behaviorBehavior. The dogsDog have adapted to omnivorous dietsDiet containingTaurine taurine-abundant meat andStarch starch-rich plant ingredientsIngredient. By contrast, domestic catsCat must consumeAnimal animal-sourced foodsFood for survivalSurvival, growthGrowth, and developmentDevelopment. Both dogsDog and catsCat synthesizeVitamin vitamin C and many amino acids (AAs, such as alanine, asparagine, aspartate, glutamate, glutamine, glycine, proline, and serine), but have a limited ability to form de novo arginineArginine and vitaminVitamin D3. Compared with dogsDog, catsCat have greater endogenousEndogenous nitrogenNitrogen losses and higher dietary requirementsRequirement for AAs (particularly arginineArginine, taurineTaurine, and tyrosineTyrosine), B-complex vitaminsNiacin (niacin, thiamin, folateFolate, and biotinBiotin), and cholineCholine; exhibit greater rates of gluconeogenesisGluconeogenesis; are less sensitive to AA imbalances and antagonism; are more capable of concentrating urineUrine through renal reabsorption of waterWater; and cannot tolerate high levels of dietary starchStarch due to limited pancreatic α-amylase activity. In addition, dogsDog can form sufficient taurineTaurine from cysteineCysteine (for most breedsBreeds); arachidonic acidArachidonic acid from linoleic acidLinoleic acid; eicosapentaenoic acid and docosahexaenoic acidDocosahexaenoic acid from α-linolenic acid; all-trans-retinol from β-carotene; and niacinNiacin from tryptophanTryptophan. These synthetic pathways, however, are either absent or limited in all catsCat due to (a) no or low activities of key enzymesEnzyme (including pyrroline-5-carboxylate synthase, cysteineCysteine dioxygenaseDioxygenase, ∆6-desaturase, β-carotene dioxygenaseDioxygenase, and quinolinate phosphoribosyltransferase) and (b) diversion of intermediates to other metabolic pathways. DogsDog can thrive on one large mealMeal daily, select high-fatFat over low-fat dietsDiet, and consume sweet substances. By contrast, catsCat eat more frequently during light and dark periods, select high-proteinProtein over low-protein dietsDiet, refuse dryFood foodDry food, enjoy a consistent dietDiet, and cannot tasteTaste sweetness. This knowledge guides the feedingFeeding and care of dogsDog and catsCat, as well as the manufacturing of their foodsFood. As abundant sources of essentialEssential nutrients, animal-derivedAnimal foodstuffsFoodstuff play important roles in optimizing the growthGrowth, developmentDevelopment, and healthHealth of the companionCompanion animalsAnimal.