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Dog Digestive System – Organs, Hormones, Gut Health & FAQs

↯ Key takeaway points

  • Dog digestive system involves various organs and starts from the mouth.
  • It breaks down food into nutrients required for energy, repair, and growth.
  • It's important to be aware of the different stages of a dog's digestive system for maintaining its health and identifying any issues.
  • Digestion begins in the mouth with minimal enzyme production in the saliva.
  • Dog digestive system disorders are common and have nonspecific symptoms making it difficult to diagnose at home.
Written by Jay
BsC (Hons) Animal Behaviour & Welfare graduate with a passion for advocating for misunderstood animals.
Zoo and wildlife doctor in veterinary medicine passionate about animal welfare and preventive medicine.
Published on
Wednesday 17 June 2020
Last updated on
Tuesday 6 June 2023
dog digestive system
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The dog’s digestive system is responsible for processing food, starting from the mouth down to the rectum and anus. The organs involved in the digestive system include the esophagus, liver, pancreas, stomach, intestines, and gallbladder. This system plays a crucial role in breaking down food into essential nutrients that provide energy and support cell growth and healing.

Disorders in the dog’s digestive system can have severe effects on its overall health and happiness. Therefore, it is vital to maintain a healthy digestive system to prevent such issues from occurring and ensure that your furry friend leads a long and fulfilling life.

Stages of The Dog Digestive System

In order to maintain a healthy dog digestive system, it’s important to be aware of the different stages and what their significance is. Knowledge of your dog’s digestive system will also help you to identify when something is wrong, and when you need to seek out veterinary advice.

dog digestive system diagram
It’s important to be aware of the different stages of your dog’s digestive system.

Stage 1: Mouth and Esophagus

Digestion begins with the mouth. Unlike humans, the salivary glands of dogs don’t secrete many digestive enzymes – there is minimal production of amylase, but nothing more. The sole digestive function of saliva in a dog’s mouth is to lubricate the food and to protect the oral mucosa whilst eating. This means that dogs don’t need to chew their food to mix enzymes with it.

Food moves down the esophagus due to esophageal peristalsis, the contraction of circular muscle that pushes the food towards the cardiac sphincter. The esophagus consists of three structures: the upper esophageal sphincter, the body, and the lower esophageal sphincter. Two layers of striated muscle protect this organ.

saliva in a dogs mouth
Digestion begins with the mouth.

Stage 2: Stomach

Once the food arrives at the cardiac sphincter it enters the stomach. Gastric folds on the interior surface of the stomach help to grind and break down food. These folds enable the stomach’s expansion when a large meal is eaten. The stomach lining secretes four substances: mucus, hydrochloric acid, pepsinogen, and gastrin.

Gastrin is the primary hormone produces by the stomach cells. It controls hydrochloric acid secretion and stomach contractions. Hydrochloric acid interacts with pepsinogen and converts into pepsin, a digestive enzyme that breaks down proteins. Once the food is broken down by pepsin into chyme, it slowly exits through the pyloric sphincter and passes into the duodenum, the first part of the small intestine.

Stage 3: Small Intestine

The small intestine is comprised of three parts: the duodenum, ileum and the jejunum. Each segment has a different structure and function, but the collective function of the three segments is to complete digestion to allow for the absorption of nutrients.

At the beginning of the duodenum, the pancreas supplies acid-neutralizing sodium bicarbonate and digestive enzymes. Two hormones control these substances: pancreozymim and secretin, which come from cells in the small intestine. Sodium bicarbonate neutralizes the acidic chyme and helps to create an ideal environment for enzymes to function. These enzymes include amylase for carbohydrate digestion, protease for protein digestion, and lipase for fat digestion.

The villi and microvilli absorb nutrients. Microvilli produce digestive enzymes, absorb nutrients and block the absorption of any waste products. By the time the chyme reaches the end of the small intestine, up to 80 percent of the water is absorbed. Once absorption is complete, material enters the ileocaecal valve.

Stage 4: Large Intestine

The large intestine is the terminal portion of the intestinal tract. It consists of the cecum, colon, and rectum. The three main functions of the large intestine are the fermentation of indigestible food, recovery of water, and storage of feces.

The cecum absorbs the remaining water and salts and mixes the chyme with lubricating mucus. The colon, the largest portion of the large intestine, ferments unabsorbed material. Unlike the small intestine, the colon doesn’t play a major role in the digestion of food. Finally, the rectum stores the formed feces. Feces consist of about 60 to 70 percent water. The remaining percent is made up of dead bacteria, inorganic material, and food.

Ensuring a Sound Digestive System

It is vital to ensure that you look after your dog’s digestive system as it plays a huge role in your pet’s overall health and well-being. Selecting the best food, monitoring your dog’s stool, annual veterinary health checks, and prebiotic supplements are elements you should consider when caring for your dog.

Selecting the Right Food

Choosing the right food for your dog is essential for keeping their digestive system healthy. But with so many options out there, it can be overwhelming to know where to start. When looking for good dog food, be sure to consider the quality of the ingredients, the type of food (wet or dry), and how it fits into your budget. Doing your research can help you make the best choice.

A balanced diet for your dog should include high-quality protein, whole grains, healthy fats, and essential vitamins and minerals. When you switch to a new food, be sure to do it gradually to avoid upsetting your dog’s stomach. Start by mixing a small amount of the new food with their current food and gradually increase the amount over a week until they are eating only the new food.

By using simpler language and explaining jargon terms, this statement is now easier for a non-scientific audience to understand.

Noticing Your Dog’s Stool

Your dog’s poop can actually tell you a lot about their health! When their digestive system is working well, their poop will look normal and healthy. But when something is off, you might notice some changes. Here are some things to look out for:

First, check the frequency of your dog’s poop – they should go at least once a day. If they’re going less often or not at all, it could be a sign of constipation. If they’re going too often, it could be a sign of diarrhea.

Next, check the color – it should be a normal brown color. If it’s red or black, that could indicate there’s blood in the stool. If it’s gray or yellow, there might be a problem with your dog’s liver or pancreas. And sometimes, green poop could just mean they ate some grass!

Lastly, check the consistency – it should be firm, but not too hard or too runny. Hard poop can mean they’re dehydrated, while runny poop could mean their large intestine isn’t absorbing enough water during digestion.

Visiting the Vet

Regular visits to the vet are important for your dog’s overall health, and this includes checking on their digestive system. Your vet can help catch any health issues early on, which is key to successful treatment. So make sure to schedule a check-up at least once a year!

If you suspect something is wrong with your dog’s digestion, don’t hesitate to seek veterinary advice. And if your vet asks you to bring in a stool sample, don’t worry – it’s a common request! Just try to collect the sample as soon as possible, ideally within the last four to six hours. You can use a sealed baggie to collect a small amount of poop, about the size of a sugar cube or half a teaspoon


Probiotics are live, beneficial bacteria that are given for maintaining intestinal microbial balance. When a dog is stressed or unwell, the balance between healthy and unhealthy microbes in the gut alters considerably. Probiotics usually contain bacteria that are naturally found in the dog’s gut, including Lactobacillus, Enterococcus, and Bifidobacterium. When choosing a probiotic, you should look for a few things, for example:

  • List of the specific probiotics used in the product, including the strain. Not all microbes of the Lactobacillus genus, for example, have probiotic activity. Some are anti-inflammatory, while others are immune stimulants.
  • Guaranteed analysis of the number of live strains that are in the product, and that the life of the probiotics is guaranteed at the end of its shelf life. By the time you purchase and use the product, the live bacteria may have already died.

Prebiotic fiber is a non-digestible, soluble fiber that feeds beneficial bacteria colonies in the gut. This fiber helps to increase the number of good bacteria in the digestive system. Foods like soybeans, legumes (peas, beans, lentils), oats, and beet pulp are excellent sources of prebiotic fiber. Bacteria in the gut ferment the fiber. This produces short-chain fatty acids. These serve as the primary fuel for cells in the colon. Increased amounts of short-chain fatty acids and increased numbers of good bacteria support good gastrointestinal health in dogs.

Signs of Dog Digestive System Disorders

Dogs can have a lot of different digestive problems, so it’s important to know what signs to look for if your pet isn’t feeling well. Unfortunately, many symptoms of digestive problems are hard to identify, so it can be difficult to diagnose your dog at home. If your dog keeps showing the same symptoms or has more than one of the symptoms listed below, it’s a good idea to take them to the vet.

Excessive Drooling

The medical term for excessive drooling in dogs is ptyalism. A common cause of ptyalism in dogs is nausea. Nausea is often triggered by irritation of the stomach and precedes vomiting. Excess saliva is produced in order to protect the mouth. Saliva also protects the throat from stomach acid. Ptyalis and vomiting, therefore, tend to come together, but excessive drooling is not always a symptom to take lightly.

Excessive drooling in dogs is also a symptom of various metabolic disorders, obstructions in the esophagus or mouth, mandibular fractures, megaesophagus, and gastric dilation, amongst many other disorders.

excessive drooling in dogs
Excess saliva is produced in order to protect the mouth.


Loose stool and diarrhea are clear signs that there is something wrong with your dog’s digestive system. Different forms can indicate different health problems.

Acute diarrhea

Acute diarrhea is a common affliction in dogs. Diarrhea is characterized by frequent watery stools, often accompanying a strong odor or color change. A dog suffering from diarrhea often develops a sore bottom. Your dog might scoot or rub their rear end across the floor or carpet to try to ease their symptoms. There are several reasons why a dog suddenly suffers from diarrhea. Stress is one of the most common causes of acute diarrhea. This includes stressors such as travel, boarding, and introduction to new pets. However, most cases are put down to these triggers:

  • Food intolerances
  • Viral or bacterial infections
  • Stress
  • Sudden dietary changes
  • Dietary indiscretion
  • Systemic illnesses
  • Intestinal parasites

Chronic diarrhea

Chronic diarrhea is diarrhea occurring for more than three weeks. This type of diarrhea is dangerous. Not only is it uncomfortable for your dog, but it also frequently causes dehydration. Symptoms found when chronic diarrhea originates in the small intestine include weight loss, gaseous sounds from the gut and black, tarry stool.

Symptoms found when chronic diarrhea comes from the large intestine include blood in the feces, straining and urgency, and pain while defecating. The small intestine produces an abnormally large volume of feces, whereas the large intestine tends to produce less, but more often. Chronic diarrhea must be addressed by a veterinarian. Your pet may require electrolytes and water via a drip to be properly rehydrated.


A lack of defecation from your pup is another strong sign that something is wrong with their digestive tract.

Acute constipation

Constipation is the inability to produce a normal amount of stools. For dogs, this should be once or twice a day. Dogs with constipation will strain to defecate, produce very hard stools, or not defecate at all. In some cases, dogs vocalize whilst straining to defecate due to the discomfort and pain involved.

Lack of fiber in the diet is a common cause of acute constipation. As with humans, a lack of fiber is often the culprit. Dietary fiber plays a vital role in the digestive health of dogs. Not only does it fuel the colon cells, but it also keeps bowel movements regular and healthy. Most commercial pet foods contain at least 5 percent crude fiber, which is usually enough for the healthy dog. If you suspect that your dog is not getting enough fiber in their diet, consider adding small amounts of high-fiber ingredients to their meal. Healthy options include green beans and wheat germ.

Dehydration is another common cause of acute constipation. This occurs when the body loses more fluid than it is taking in. Water is necessary for every vital body function, especially when it comes to digestion. In order to retain water, your dog’s digestive system will make up for the losses by producing hard stools without much water in them.

Chronic constipation

Chronic constipation results in a condition called obstipation. Obstipation occurs when dry, hard fecal matter compacts the digestive tract. This prevents the dog from defecating at all and is painful. Obstipation denotes a loss of control over the large intestine. Ultimately, it culminates into a syndrome known as megacolon. To diagnose your dog, your veterinarian will ask for their history, carry out a physical examination and conduct radiography. Treatment involves a subtotal colectomy and a high fiber diet.

dog digestive system disorders
Be aware of the signs when something is wrong with your pet.

Vomiting Or Regurgitation

Vomiting is the forceful ejection of stomach contents. There’s often a heaving motion wherein the abdominal muscles contract repeatedly before the stomach contents are expelled onto the floor. Vomit usually contains partially-digested food, yellow bile, and smells foul. Usually, when a dog vomits once and continues having normal bowel movements afterward, they recover without incident. However, chronic vomiting and vomiting alongside other worrying symptoms should be evaluated by a veterinarian.

Chronic vomiting indicates a variety of conditions, including ingestion of toxins, dietary allergies, inflammatory bowel disease, and metabolic disease. The wide array of causes means that it’s difficult to pinpoint the exact problem at home, so an appointment with your veterinarian is always the best course of action.

Regurgitation in dogs is a passive process that comes with little warning. When a dog regurgitates, chances are that they will open their mouth and expel water or undigested food that they just ate. The contents, called regurgitus, typically contain food, saliva, and mucus, but no bile. Regurgitation points to serious underlying conditions more than vomiting does and the problem usually lies with the esophagus. Pharyngeal dysphagia, vascular abnormalities, esophagitis, hypoadrenocorticism, lead toxicity, and megaesophagus are just a few of the possible causes of regurgitation in dogs. Obstructions in the esophagus also cause problems with regurgitation.

Loss Of Appetite

Loss of appetite is a common symptom that could be caused by many different illnesses. Sometimes, it could be because your furry friend is a picky eater, while other times it could indicate a serious underlying issue. As a pet owner, you know your furry friend best, so it’s up to you to determine whether their lack of appetite is normal for them or not.

If your dog has an upset stomach or is stressed, they may not eat much, but they should start eating again within 24 hours. However, if your pet has not eaten for more than 48 hours, it’s time to see the vet because it could be a sign of a serious problem. Your veterinarian may provide your pet with intravenous fluids with electrolytes if they haven’t been drinking for over a day. In severe cases, they may use a feeding tube. Whatever the cause of the loss of appetite is, the underlying problem must be addressed in order to help your furry friend get better.

Abdominal Pain And Bloating

Abdominal pain is another general symptom. Pain and bloating occur from things as simple as overeating. The symptoms also suggest a myriad of life-threatening diseases too. Because of this, it’s important that you ask for veterinary advice as soon as possible.

The signs of abdominal pain include unusual posture, drooling, tenderness and lethargy. When these symptoms occur repeatedly it’s called “acute abdomen.” Acute abdomen is a symptom of several gastrointestinal illnesses. This includes gastritis, inflammatory bowel disease, intestinal inflammation, malabsorption, and gastrointestinal obstructions.

Dog Digestive System – FAQs

Need to know something else about the dog digestive system? Our FAQ has all the answers you need. If in doubt about your dog’s digestive health, always consult your veterinarian for advice before implementing any significant changes to how you care for your dog.

How Long Does it Take for Food to Pass Through the Dog Digestive System?

On average, canines digest food much quicker than humans. While humans require 20 to 30 hours to fully digest a meal, dogs only need six to eight hours. In some cases, digestion takes up to 12 hours but is sometimes as quick as four.

Several factors determine how long it takes for your dog to digest a meal. As a general rule, the older and larger your dog is, the longer digestion takes to complete. As a dog ages, their metabolism slows down. In addition, the amount of exercise your dog has each day impacts digestion – the more energy your dog uses, the quicker their body needs to make use of the food they consume. Finally, the type of food your dog eats will also determine how quickly the digestion process completes itself. Typically, protein digests faster than grains, so a diet high in protein is more digestible.

How do you know if your Dog has Digestive problems?

Digestive problems in dogs often manifest through a wide range of symptoms. The most common symptoms include constipation, diarrhea, drooling, vomiting, regurgitation, lack of appetite, abdominal pain and bloating. Some digestive problems resolve within 24 hours. However, because more serious health conditions result in dangerous symptoms like dehydration and anorexia, you should always take your pet to the vet with any concerns.

In order to identify what digestive problems your dog is facing, your veterinarian will carry out one of or a few of these tests:

  • Complete blood cell count (CBC) – used to identify infections
  • Urinalysis – used to identify urinary tract infections and dehydration
  • Abdominal ultrasound – used to identify intestinal obstructions
  • Abdominal X-ray – used to identify intestinal obstructions

How long are a dog’s intestines?

The average length of the intestines varies slightly depending on the size of the dog. However, the average length of the dog’s small intestine is reportedly 4.0 meters or 13 feet. The large intestine is larger in diameter, but shorter, measuring around 0.6 meters or 2 feet in length.

How can I Improve my Dog’s Digestion?

Maintaining healthy digestion doesn’t have to be a difficult task. Fortunately, there are many ways to help your dog’s digestive system to stay healthy including a balanced diet and increased fiber. In order to improve your dog’s digestion, it’s crucial that you understand what makes a sound digestive system. A healthy dog digestive system has healthy immune cells, a good balance of beneficial bacteria in the gut is and given a suitable diet.

Always provide a balanced diet for your dog, ideally complete with high-quality protein, fat, and micronutrients. If in doubt about your pet’s diet, ask your veterinarian for advice.

Prebiotic fiber is a great addition to your pet’s diet to improve their digestion. Prebiotics are soluble fibers that feed the beneficial bacteria residing in the gut. Suitable prebiotics include soybeans, legumes, and oats. Some commercial dog food incorporates these prebiotics into their ingredients. Fiber in general also helps to resolve constipation problems.

Maintaining good dog digestive health is important for the wellbeing and health of your pet. Not only will you help to prevent potentially life-threatening illnesses, but you will ensure that your dog has the energy and nutrients to enjoy life to the fullest.

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