Posted by Pet Honesty on

The Dog Digestive System: Everything You Need to Know

Table of Contents

Ask any vet, and they will tell you that a healthy digestive tract is the best marker for a healthy dog. From vigorous appetite to regular bowel movements, your dog’s diet and digestion are what keeps him at the top of his game. While a daily dog digestion supplement can help keep your pup in tip-top shape, his daily diet will also have a major impact on his overall digestion. As a dog owner, one of the best ways you can do to keep your dog healthy and happy is to pay attention to his daily digestion. Whether you are new to monitoring your dog’s digestive health, or if you need a little refresher course, this article has everything you need to know about the dog digestive system.  

The dog digestive system is complicated, to say the least. Many small intricacies help keep your dog’s insides running smoothly. Dogs, as descendants of one of the world’s most magnificent apex predators, are designed to consume and burn food much like a high-end race car uses fuel. The digestive system of a dog can be divided into four main categories consisting of: the mouth and esophagus, the stomach, the small and large intestine, and the colon. Each piece of this intricate puzzle has its own specific function as it relates to the digestive process. Below are the primary subdivisions of a canine digestive tract and their rudimentary functions.

The Mouth and Esophagus 

For the digestive process to begin, your dog must eat. Appetite spurs your dog to consume food, and as he does, it is chewed in the mouth and then swallowed where it is passed down the esophagus and into the stomach. Your dog uses his front teeth to grab food and then pulls his food to the back of the mouth where molars grind up the food into smaller chunks.  

The appetite and nutritional needs of a dog will vary on a case by case basis, but one cup of dry food for every 30 pounds seems to be an accepted daily standard of how much food to give your dog. If you are still unsure how much to feed your dog, talk to your veterinarian for further assistance.  

The esophagus is lubricated by saliva which allows the food your dog chews to easily slide down his muscled throat passage. For humans, saliva helps to break down the food we consume, but for dogs, saliva is more of a lubricant as it lacks the same enzymes and bacteria that human saliva contains. 

The Stomach 

Once food passes through the esophageal passage, it ends up in the stomach. In humans, food doesn’t stay in the stomach for very long, typically only about a half an hour on average. The dog digestion time where food remains in the stomach can be upwards of twelve hours. Food can be stored in the stomach for anywhere between 4 and 12 hours, depending on the caloric needs of the animal.  

The stomach is an integral part of the dog digestive system where food is broken down from bite-size chunks into more of a digestible mush.  Although the process of actively breaking down food into digestible caloric fuel does not begin until the food is pulled into the small intestine, the role the stomach plays in changing the consistency of the food is integral to the next steps of the digestive process. 

In dogs, the stomach is more of a storage facility wherein the body can pull food to be converted into energy as it is needed. This specific design comes from a dog’s genetic ancestry wherein wolves would potentially have to go long periods of time without eating. As a result, dogs can conserve their energy and keep their caloric output low, allowing them to save up and store food until they need it.  

A dog’s stomach can expand to extraordinary sizes to accommodate this type of eating pattern. While your dog should never need to use this incredible function of his digestive system, it does give a more in-depth insight into how your dog digests food daily. The caloric requirement of your dog’s needs is entirely dependant on their output of energy, and while we will discuss this aspect of the digestive system later, for now, it is the perfect transition into the role of the intestines. 

The Intestines

In dogs, the small intestine is the star of the digestive system. The small intestine can be up to three times as long as the dog it inhabits, and it is divided into three subsections. The first section of the small intestine is the duodenum, which contains small ducts where chemicals can be introduced to the food to aid in the dog digestion process. The duodenum is attached to the gallbladder, liver, and pancreas so that secretions of digestive enzymes and bile can be absorbed by the food and be prepared for intake. 

The jejunum is the second, and longest section of the small intestine. This is where food, after being turned into a nutrient-rich mush, is finally absorbed by the body. Nutrient absorption is the key to the digestive process, as this is how your dog turns food into energy. A vast collection of small extremities, called villi, hang below the surface of the jejunum and like tiny tentacles stick to the passing particles.  

As the villi absorb the nutrients from the food, a collection of leftover waste begins to form which is passed on through the last section of the small intestine called the ileum. The ileum is the shortest section of the small intestine and is essentially the connective tissue between a dog’s small intestine and large intestine.  

The Colon 

In dogs, the large intestine is also the beginning of the colon.  After food is passed from the ileum into the large intestine, it begins to form and take shape.  Once the remnants of the digested food enters the large intestine, the substance is now fecal matter. 

One of the primary responsibilities of the large intestine is to remove moisture from fecal matter to prevent the body from becoming dehydrated. The large intestine, comprised of the ascending and descending colon, is where fecal matter is stored until it is expelled from the anus. 

Anatomy is just the beginning

The anatomy of your dog’s digestive tract is an essential factor in understanding the mechanics of how your dog’s digestive system operates. However, there are many other factors at play when it comes to how your dog digests his food. The speed, effectiveness, and regularity of your dog’s digestion are determined by a combination of breed, weight, age, activity level, and even the kind of food they are consuming. 

How size and age affect digestion

Size is one of the most significant determining factors for how long it will take a dog to digest their food. It should come as no surprise that a puppy needs to consume and digest food on a more regular basis than a full grown adult dog, and because a puppy is continually increasing in size, it requires a more nutrient-rich diet. A higher frequency of ingested food and a more nutrient-rich diet means that puppies will tend to have a faster digestive time table than most full grown dogs.  

Remember the bit about your dog’s intestinal tract typically being 3 times as long as they are?  This is an excellent example of how a dog’s physical size plays into their personal digestion timeline. The smaller the intestinal tract, the quicker the food will be digested. In other words, the smaller the dog, the faster food will go from being consumed to expelled.  

A full-grown adult dog can range anywhere between 5 and 120 pounds depending on the breed, and because breed type plays a significant role in determining how big a dog will get, breed will give an owner an idea for how often your dog needs to be fed and walked.  

Age is the last key piece when it comes to digestion. As canines age, their metabolism slows down, and over time, the digestion process becomes a more time-consuming endeavor. Between what we know about age, size, and breed, we can determine that the larger and older the dog, the longer the digestion process will take. 

How exercise plays a role

As alluded to earlier, dogs are built to withstand long periods between meals. Thanks to their genetic inheritance, a dog’s digestive system is constructed to handle a predominantly carnivorous diet.  

Dogs can store massive quantities of food in their stomach, which is designed to expand well beyond its typical daily limits to accommodate for long periods without food. As we know for our anatomy lesson above, a dog’s digestive system will only use as much food as needed for the physical output of energy, keeping the rest of the food stored in the stomach until more caloric energy is required.  

This is why exercise is another essential piece in the puzzle of canine digestion. The more energy a dog uses, the more rapidly their body will take the food stored in the stomach and send it to the intestinal tract where it can be turned into caloric energy to supplement the output of physical strength.  

Exercise is an integral part of your dog’s digestive health and to help prevent digestive problems. For dogs, food is caloric fuel that should be burned off actively rather than stored and passively doled out due to a sedentary lifestyle.  

Your dog’s age and breed will determine how much activity level they require, and it is of the utmost importance for their digestive health and well-being that you as their owners take charge of their physical schedule. Long walks, running, and rigorous play are all enjoyable activities that will help your dog work up an appetite and stay regular. Although exercising before meals is best, if you do exercise with your dog after he eats, be sure to avoid vigorous play as it will likely cause canine indigestion.

are they eating?

It may seem obvious, but different foods are digested at different speeds. Typically any dog food that contains a large amount of grain will be digested slower than food that is more protein-rich.  A dog’s digestive system craves a protein-rich diet as the high caloric content fuels the active lifestyle of canines.  

In terms of the everyday food we feed our dogs, grain is a staple ingredient for most brand name dog foods. Dry kibble is often heavily grain-based, while most wet canned food has a higher protein and calorie content. In other words, wet food will usually yield a faster digestion time, whereas dry food will yield a slower caloric burn.

There is no right or wrong food to feed your dog, so long as it is food that is designed for dogs.  It is important to find the right food for the specific dietary needs of your dog based on age, weight, and breed. Take time to speak with your vet about any dietary restrictions your dog should adhere to, and do your best to stay away from overly processed food sources. A well-balanced diet is a critical part of keeping your dog’s digestion healthy and regular.

Caring for your dog’s digestive system is one of the most powerful elements of a preventive health care routine. Understanding the anatomy of your dog, and how those parts of the body play a role in the digestive system, is a wonderful advantage in understanding how to care for your dog long term. This knowledge, however, is no substitute for the extensive understanding and skill your vet possess regarding the intricate workings of your dog’s body. Always be sure to consult a vet whenever you may suspect a health issue in your dog.  Whether you are looking for a treatment for dog diarrhea or you’re on the hunt for a new probiotic or cranberry supplement for dogs, your vet will be there to guide you along the way. With the understanding you have gathered from this article regarding the dog digestive system, you are better suited to help your dog live a healthy and fulfilling life.


Camille Arneberg and her dog
Camille is a co-founder of Pet Honesty and VP of Pup Parent Education. After watching her own family dog suffer from joint issues for years she became passionate about improving dogs' quality of life. With the help of a team of veterinarians and dog nutritionists she now helps educate other dog owners about the small but powerful things they can do to positively impact their dogs' health and wellness! She lives in Austin, TX and loves cuddling puppies, being outside and reading.