One of the common struggles facing dog owners today is that of maintaining the digestive health of their canine. Upset stomach, loose stools, flatulence, vomiting, or even bloat can afflict dogs of all genetic heritages (with the exception of bloat, which primarily affects large and giant breed dogs). Certain breeds—including the German Shepherd Dog—may show a propensity for sensitive stomachs (which is one reason why GSW carefully selects their dogs from proven bloodlines), but digestive problems of some kind will be encountered by pet owners at one point or another.
While many people accept large, soft stools or flatulence as “normal” for their dogs, such issues should not be common occurrences in healthy digestive systems. This first blog will discuss the normal, healthy canine digestive system. Future blogs will discuss diet, probiotics, intestinal disturbances, and bloat.
The Canine Digestive System
The digestive system of a healthy canine is specialized, elegant, and highly efficient. The gastrointestinal tract starts with the dog’s mouth. Dogs have the taste palate of carnivores, which includes a low sensitivity to salt and a higher taste sensitivity for sweet (such as ripe fruit—a seasonal treat that provides quick and easy energy). Their saliva contains enzymes for destroying bacteria, plus a lubricating agent that coats large chunks of food. The adult dog generally has 42 teeth, which contain large canines for grasping prey, incisors for shredding meat off the bone, and sharp premolars and molars for shearing off meat and crunching up bones. The dog’s jaw hinges open widely, allowing them to open their mouths vertically to a greater angle than we can. The ‘hinge’ on the canine jaw prevents side-to-side motion, allowing only for vertical opening. In characteristic carnivore style, food can be torn off into chunks and be swallowed in large gulps with minimal chewing, passing down the elastic esophagus into the dog’s simple yet muscular stomach.
The dog’s stomach is highly elastic, allowing it to stretch considerably to accommodate the incoming chunks of food. Hydrochloric acid, enzymes, and the squeezing motions of the stomach help break down food so that it can be further digested in the intestines. Unlike humans, dogs only produce stomach acids when they eat or in anticipation of food. This stomach acid is incredibly powerful, making it perfectly suited to dissolving meat and bone (but less suited to helping break down carbohydrates, which require a less acidic pH. The stomachs of herbivores, for example, have a pH of 4-5. Dogs have a pH of 1 in their stomachs.).
As the broken-down food moves from the stomach into the small intestine—which in the dog is relatively short compared to the more lengthy intestines of omnivores and herbivores—the dog’s pancreas, liver and gallbladder release enzymes (pancreas) and bile (liver and gallbladder) to assist with digestion. Protein- and fat-digesting enzymes are released, along with small amounts of an enzyme that breaks apart any starches. The bulk of the nutrients are absorbed here in the small intestine, not in the stomach.
A plethora of beneficial bacteria reside in the intestines and help with this process. These microorganisms aid in digestion, and also make certain vitamins for the dog, particularly B vitamins. These good bacteria also help prevent the colonization of bad bacteria and yeast. These good bacteria are often called probiotic bacteria. Dogs have their own unique intestinal flora (microorganisms), and lack the helpful bacteria that break down the cellulose found in plant matter (an adaptation that is found primarily in herbivores, as opposed to carnivores like dogs).
The small intestine segues into a short, smooth large intestine (unlike the much longer, sacculated large intestines of omnivores and herbivores). The large intestine simply reabsorbs water and electrolytes, forming stool from the solid waste left behind. This waste moves into the rectum and out the anus during a bowel movement. As it does so, it passes the anal glands, sacs situated on either side of the dog’s anus. These sacs are emptied as the dog poops, their contents squeezed out naturally during the bowel movement.
This, in a nutshell, is the canine digestive system. Next blog, we will discuss the diet best suited for this particular digestive system.