Knowing how long it takes for dogs to digest food is important. Proper nutrition is the brick and mortar of a healthy and long life.
However, even the ideal nutrition will not suffice if the digestion processes are compromised.
Knowing how your dog’s digestion apparatus works is therefore equally important as knowing which foods are safe and which are not.
In this article, we will take you on the same trip food goes – starting from the mouth down the esophagus, then into the stomach, and intestines up until the final exit.
We will also explain how digestion occurs in dogs and how long does it take them to digest food.
How Does a Dog's Digestive System Work?
Digestion in dogs is a complex process that starts the moment the food enters the dog's mouth. As the food moves through the digestive apparatus, the necessary nutrients are absorbed into the bloodstream and the unnecessary are expelled in the form of feces.
To make things simpler, you can imagine the digestive system as a long tunnel with two openings – an entry point (the mouth) and an exit point (the anus). Different digestion processes occur in different parts.
Let’s take a look into each section.
Entering Your Dog's Mouth
As mentioned, digestion starts the moment the food enters your dog's mouth. In the mouth, the digestion processes are based on mechanical grinding and moisturizing.
The dog’s teeth are well-developed, strong, and capable of tearing the food into small pieces. Dogs have 42 teeth that are much sharper, stronger and leaner than our set of only 32 teeth. However, unlike us, dogs cannot chew side-to-side, only up and down.
The physical presence of food inside the mouth and its taste and smell stimulate increased saliva secretion. The dog’s saliva contains mucus which acts like a lubricant. It basically coats the food and makes it glide easily during swallowing.
Unlike the saliva of other animals (and humans), the dog’s saliva does not contain any enzymes meaning the digestion processes in the mouth are purely mechanic.
This describes how the digestion process should look. However, dogs especially the ones with voracious appetites, rarely chew their food. Instead, they gulp down food, thus, swallowing entire (non-grinded and non-coated) chunks.
Entering Your Dog's Esophagus
Once mechanically processed and moisturized, the food enters the esophagus or gullet. The esophagus is literally a strong and narrow tube with a robust muscular layer whose contractions push the food down into the dog's stomach. The pushing process is actually a wave-like motion called peristalsis.
The esophagus’ only purpose is connecting the mouth and the stomach, there are no actual digestion processes in this part of the gastrointestinal apparatus.
Entering The Dog's Stomach
The stomach is where most of the digestion occurs. The stomach has several different roles:
- Storage. Basically, the food accumulates before it is being digested
- Mixing bag. Like a cement mixer, the food is mixed with various digestive enzymes
- Regulatory valve. The stomach controls the food flow rate.
The most amazing thing about the dog’s stomach is its ability to produce a substantial amount of strong acid (up to 100 times the amount of stomach acid in humans). Therefore, the dog’s stomach can digest edible and non-edible items the human stomach could never process.
The stomach secretion contains acid, digestive enzymes, and mucus. The three major protein-digesting enzymes are:
Some of the digestive enzymes are secreted in a non-active state and then activated by the hydrochloric acid (a protection mechanism so they could not destroy the cells where they are produced). For example the pepsin’s inactive form is pepsinogen.
Mucus also plays a protective role. It covers the stomach lining to prevent it from being damaged (digested) by its own enzymes.
The exact composition of the stomach secretion (enzyme to acid to mucus ratio) is determined by the amount and composition of ingested food and is regulated by a vast network of nerves and hormones.
The mixture of half digested food and stomach secretions is called chyme (thick and milky liquid).
Once the food is turned into a chyme, the stomach’s wall (which is quite muscular especially in the pyloric region) pushes it into the first part of the small intestine, known as the duodenum. The more liquefied the chyme is, the easier it will pass into the duodenum.
Entering The Dog's Small Intestine
In dogs, the small intestine accounts for 25 percent of the gastrointestinal tract’s overall volume. Although called small, this intestine does a big job.
The main digestion site of the small intestines is the duodenum. In the duodenum the chyme is mixed with more enzymes produced in the pancreas.
The pancreas produces three different types of enzymes for breaking down three different nutrient types:
- Proteases – which continue the protein digestion
- Amylase – for digesting carbohydrates
- Lipase – for digesting fats.
In addition to enzymes, the so-called pancreatic juice contains bicarbonates which neutralize the acidity of the chyme making it friendlier to the intestinal environment.
At this point, the chyme is also mixed with bile (secreted in the liver and stored in the gall bladder).
Bile contains detergent-like salts that transform fats into tiny globules thus making them more susceptible to the lipase’s activity. It also contains pigments which are responsible for the characteristic color of the feces.
Once the chyme is well-mixed and broken down to simple components, the necessary nutrients are absorbed through the intestinal wall and into the bloodstream.
Most of the digestion’s end products are brought to the liver, while fat is absorbed in the lymph vessels and then transferred to the bloodstream.
The absorption processes take place along the small intestine’s full length. Their lining has folds and villi (finger-like projections) whose presence increases the absorption surface.
Entering The Dog's Large Intestine
When the chyme reaches the large intestines almost all nutrients are digested and absorbed. Consequently the chyme does no longer look like a milky fluid, but is in fact a thick paste.
The large intestine is responsible for two processes: re-absorbing water and fermenting dietary fibers.
Once these processes are performed, the food is officially transformed into feces. Feces are made of 60 to 70 percent water, some undigested food, inorganic material (non-digestible food components), and dead bacteria.
The undigested food part is comprised of nutrients the dog’s body cannot absorb because of their low-digestibility level or cannot be broken down.
For example, the presence of undigested vegetable chunks in a dog's feces does not mean the vegetable was not used – it means the dog utilized the absorbable nutrients and eliminated the unnecessary parts.
Exiting the Dog's Bottom
Feces are stored in the rectum and then expelled through the anal sphincter. Hopefully, the expulsion occurs when you are walking your dog and not while you are at home.
The feces or better said its basic features (color, smell, consistency, and volume) can give a lot of information on the dog’s overall health status.
Did you know? Observations on food tolerance have repeatedly shown that, when small dogs and big dogs where fed an identical diet, large breed dogs over 25 kilograms presented with softer and moister stools compared to small breed dogs under 15 kilograms.
According to a study, underlying causes for such difference has been found to be due to a larger dog's high intestinal and colonic permeabilities, prolonged colonic transit and larger caecum size compared to smaller dogs.
How Long Does it Take For Dogs to Digest Food?
The gastrointestinal transit time for dogs is between six and eight hours. In fact, the dog’s digestive tract is quicker than the digestive tract of any other mammal. In comparison, the gastrointestinal transit time in humans varies between 20 and 30 hours.
Interestingly, although the overall digestion process in dogs is much quicker than in humans, food tends to spend stay inside the dog’s stomach for a lot longer than in the human’s stomach.
Namely, in dogs based on the exact digestibility, food can stay inside the stomach for up to 12 hours. In humans, it stays for only four to five hours.
Anyway, the time it takes dogs to digest food can be affected by several factors. Some of those factors are food-related and others are dog-related.
The most important food-related factors are:
- Type of food – normally wet food is much easier and quicker to digest than kibble
- Digestibility – measure of food quality determining the amount of absorbable nutrients from the full food amount (the more digestible the food the greater its nutritional value).
On the other hand, the most important dog-related factors include:
- Breed, size, and age – every dog is different and factors like breed, size, and age affect the gastrointestinal transit rate significantly.
- Hydration level – the more water a dog drinks, the easier it will be for the food to be digested while dehydrated dogs are more prone to constipation.
- Lifestyle – physically active dogs usually have more pronounced motility rates and consequently shorter transit times than dogs with sedentary habits spending most of the time snoozing on the sofa.
- Existing health issues – certain health problems, especially the ones affecting the digestive apparatus, can affect the length of the digestion process.
Just because dogs have the shortest digestion cycles of all mammals, does not mean their digestive processes are any less complex.
Considering some foods are more easily digestible than others it is paramount you provide your dog with the right diet – in terms of both quality and quantity.
The dog’s digestive system is extremely sensitive (in spite of the sharp teeth and strong stomach acids) and can easily become irritated.
Digestive upsets are a common issue among dogs and an objective reason for visiting the vet’s office. Most of the times, they are benign and self-limiting but it is your job as a responsible dog parent to address them quickly and adequately.