Fooding for Life

Your Pet’s Digestive System

The Gut as an Ecosystem
Your fur kids’ digestive system is different than a human's and therefore dogs (and cats) process and eat differently than us. This is important to know and understand so that you can feed your fur kids the correct diet and be aware when something goes wrong.

Your fur kids’ digestive system is different than a huuman’s and therefore dogs (and cats) process and eat differently than us. This is important to know and understand so that you can feed your fur kids the correct diet and be aware when something goes wrong.

Your dog’s (or cat’s) digestive system is responsible for three things:

  • digestion of food;
  • absorption of nutrients;
  • preventing the entry of toxic, disease causing substances into the body.

All mammals have the same organ systems. They may differ slightly in some ways according to different species requirements, but mostly, they are the same. The visible components are the organs and the physical remedies your fur kid has available to digest food. There are some significant and obvious differences to what you have in your body. These are fairly easy to understand, because the differences can be observed, even by a layperson. The teeth are the most profound example. But there are also some huge differences in chemistry.

Chemistry is, unfortunately, not many people’s favorite topic of discussion. It can be complex and difficult to comprehend, even for us, but it is paramount for your ability to make sound decisions based on a good understanding of your fur kid’s needs that you do understand some of the basic chemistry. It is not our intention to make you fully educated in neither physiology nor chemistry, after all, we, ourselves, are still learning about this topic every day, but we hope that we can give you enough understanding of those topics for you to at least feel the “aha effect” when you see the perspective of why things are as they are.

Canine and Feline Anatomy
Canine and Feline Anatomy

The Mouth

In huumans, the role of the mouth, teeth and saliva play an important part in the digestion of food. In canines, this is not true. Dogs’ mouths are designed to bite off and chew large pieces and to eat quickly. Dogs have hinged jaws and large teeth, meant to ingest large chunks of meat, bones and fat products that are usually a part of the dog diet.

The mouth and teeth are the start of the dog digestive system. The food is cut, sliced or torn to the correct size by the teeth. Then it goes straight from the mouth, lubricated by saliva, and guided by the tongue, down into the esophagus.

Esophagus to Stomach

Since the mouth is not really a part of the digestive process, per se, the stomach is really more vital to the digestion of your fur kid’s food. The food passes through the esophagus on its way to the stomach.

The esophagus is the connecting tube to the stomach. It is a muscle and contracts in wave like motions, to move the food along the path to the stomach. We think the expression “wolfing down” your food, comes from this action.

Once food reaches the stomach it is processed with a high level of hydrochloric acid. This is important because this allows the breakdown of the large pieces of protein and bones that your fur kids ingest. Dogs also have a natural regurgitation instinct which allows them to spit out food that has not been processed correctly, then to re-swallow it.

The stomach works like a cement mixer, mixing and grinding and liquefying the food. The environment in your fur kid’s stomach is extremely acidic, about 1-2 PH. This hydrochloric acid is a extremely strong chemical. It would burn your hand if you were to touch it. This is way more acidic than human stomach acid which is about 5 PH.

The lining of your dog’s stomach is covered with a thick mucus. This mucus prevents the stomach from digesting itself, due to the strong acid. Together with the acid and some enzymes, the food is now ready for complete digestion in the small intestines.

Stomach to Small Intestine

After food has been processed in the stomach with the aid of the hydrochloric acid, it then passes through to the small intestine in the form of liquid. This is where the main part of the digestion occurs and where the food is assimilated into nutrients through digestive enzymes.

Basically, the small intestine is a long hollow tube. It is about four times the length of your dog’s body. Within the small intestines there are openings that let digestive juices enter from the pancreas and gallbladder.

The lining of the small intestine has millions of little finger type things called villi. These little villi increase the surface area of the small intestine to better assimilate and absorb nutrients. Almost all nutrients are absorbed from the small intestines into the bloodstream, and then travel though out the body to be used by the cells.

The main job of the small intestine is to absorb nutrients from the liquid food that has been broken down by the stomach. The canine intestinal system is shorter than that of a human. This is because for proper food digestion, as a carnivore, you fur kids’ needs a faster passing time for all the meat protein he or she eats.

Small Intestine to Large Intestine

From the small intestine, the unassimilated food passes through to the large intestine. The large intestine is the last stop before the waste is passed through rectum in the form of feces or poop.

  • The Pancreas secretes enzymes that help to further break down proteins. The pancreas is also an endocrine gland that regulates blood sugar.
  • The Gallbladder stores and regulates the release of bile. Bile is needed to break down fats.

The large intestine is also known as the colon. It has the important job of saving water and mineral electrolytes from the food that has passed through the whole system. It keeps hydration in the body at a constant level.

Bacteria ​1​ helps to break down the last, hard to digest material. Feces are formed and stored here, and await exit through the rectum, which is the last stop along the dog digestive system pathway.

Other Considerations

Canine’s actually has the shortest digestive system of mammals and it takes roughly 8-9 hours for the whole digestive process. Of course, that number is smaller for puppies, which do not have the mature system of adolescent and adult dogs.

The digestive system of canines is important and can be a good indicator when something is not working correctly or when illness is present. You should be familiar with your fur kid’s eating habits and pooping habits as well (see the article titled “What You Should Know About Your Pet’s Poop). If your fur kid is acting out of sorts, has dog bloat, or is not eating or pooping as usual, there is probably something going on inside.

A poorly functioning canine digestive system is the root cause of all disease, and directly affects your fur kid’s Immune System, on which everything else depends.

Although most dogs experience some gas, just as huumans do, particularly unpleasant gas is usually an indication of a poor diet. This can cause other problems so be consistent with your fur kid’s diet and feeding habits.

Digestive Enzymes

Digestive enzymes are enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption by the body. Digestive enzymes are found in the digestive tracts of animals (including huumans) and in the traps of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes are diverse and are found in the saliva secreted by the salivary glands, in the stomach secreted by cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the intestinal (small and large) secretions, or as part of the lining of the gastrointestinal tract.

In simple terms, the body uses enzymes to digest and use food. There are two types of enzymes that do that:  enzymes in the food itself, and enzymes that reside in the digestive organs. The body can’t produce a finite supply of enzymes – like a bank account, if you continuously make withdrawals without depositing money, you will soon be broke!

Digestive enzymes are classified based on their target substrates (roles they play in the process of breaking up the food we ate):

  • proteases and peptidases split proteins into small peptides and amino acids;
  • lipases split fat into three fatty acids and a glycerol molecule;
  • amylases split carbohydrates such as starch and sugars into simple sugars such as glucose;
  • nucleases split nucleic acids into nucleotides.

The best solution for enzyme deficiency is to feed your fur kids’ foods that already have an abundance of enzymes. Whereas processed foods are “dead”, raw and whole foods have an abundance of enzymes. In order to function optimally, enzymes work in close association with vitamins and minerals. Vitamins and minerals will also be found in abundance in raw foods.

There are many foods that are high in naturally occurring enzymes. One of the best sources is raw, green tripe – it carries a host of digestive enzymes! Fresh muscle meat is also a good source of enzymes.

Enzymes are used up faster during some illnesses, extremes in weather or strenuous exercise. Older dogs will also benefit from extra enzymes as the amount of enzymes produced in the body declines with age and this is partly responsible for age related illness and debilitation. If your fur kid has spent most of his own enzymes and he isn’t getting any in the diet, his cellular function and health will rapidly decline.

Additional Articles and Videos

Good reference articles and further reading available at:

  • Prebiotics, Probiotics And Intestinal Health Veterinary Practice News;
  • Enzymes And Your Dog, by Dogs Naturally Magazine Dogs Naturally Magazine;
  • Bacteria in the Gut: Friends and Foes and How to Alter the Balance, R. A. Rastall, J. Nutr. August 1, 2004 vol. 134 no. 8 2022S-2026S: Nutrition.Org;
  • American Society for Microbiology. “How a dog’s diet shapes its gut microbiome.” ScienceDaily. ScienceDaily, 24 January 2017, Science Daily.

References and Research

  1. 1.
    Quigley E. Gut bacteria in health and disease. Gastroenterol Hepatol (N Y). 2013;9(9):560-569.

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