Characteristics of the Digestive Tract of Dogs and Cats

As for other mammalsMammal, the digestive system of dogsDog (facultativeFacultative carnivoresCarnivore) and catsCat (obligateObligate carnivoresCarnivore) includes the mouthMouth, teethTeeth, tongue, pharynx, esophagus, stomachStomach, small intestineIntestine, large intestineIntestine, and accessory digestive organs (salivary glands, pancreasPancreas, liverLiver, and gallbladder). These carnivoresAnimal have a relatively shorter digestive tract but longer canineCanine teethTeeth, a tighter digitation of molars, and a greater stomachStomach volume than omnivorous mammalsMammal such as humans and pigs. Both dogsDog and catsCat have no detectable or a very low activity of salivary α-amylase but dogsDog, unlike catsCat, possess a relatively high activity of pancreatic α-amylase. Thus, catsCat select low-starchStarch foodsFood but dogsDog can consume high-starchStarch dietsDiet. In contrast to many mammalsMammal, the vitaminVitamin B12 (cobalaminCobalamin)-binding intrinsic factorIntrinsic factor for the digestionDigestion and absorptionAbsorption of vitaminVitamin B12 is produced in: (a) dogsDog primarily by pancreatic ductal cells and to a lesser extent the gastric mucosa; and (b) catsCat exclusively by the pancreatic tissue. Amino acids (glutamate, glutamine, and aspartate) are the main metabolic fuels in enterocytes of the foregut. The primary functionFunction of the small intestineIntestine is to digest and absorb dietary nutrients, and its secondary functionFunction is to regulate the entry of dietary nutrients into the bloodBlood circulation, separate the external from the internal milieu, and perform immuneImmune surveillance. The major functionFunction of the large intestineIntestine is to ferment undigested foodFood (particularly fiberFiber and proteinProtein) and to absorb waterWater, short-chain fatty acidsFatty acid (serving as major metabolic fuels for epithelial cells of the large intestineIntestine), as well as vitaminsVitamin. The fermentationFermentation products, waterWater, sloughed cells, digestive secretions, and microbesMicrobes form fecesFeces and then pass into the rectum for excretionExcretion via the anal canal. The microflora influences colonic absorptionAbsorption and cell metabolismMetabolism, as well as fecesFeces qualityQuality. The digestive tract is essentialEssential for the healthHealth, survivalSurvival, growthGrowth, and developmentDevelopment of dogsDog and catsCat.