Like people, dogs need to digest their food in order to absorb nutrients but the amount of time it takes for digestion to occur is not the same as humans. Cats, horses, ferrets, and dogs all digest food at slightly different rates due to their anatomy, size, diseases they may have, and other factors.
What is Digestion?
Digestion is defined as the process by which food is broken down so that the body can absorb it. Vitamins, minerals, fats, sugars, and other essential nutrients and components are contained in the food dogs eat. Without digestion, this food is not able to be absorbed in their bodies. The digestive process is therefore essential because if a dog is not able to utilize these nutrients, basic cellular and essential life functions cannot occur within their body.
How is Food Digested by Dogs?
The digestive system is much more than just a dog's stomach. It starts with the mouth where a dog chews the food it eats, then the esophagus which transports the food from the mouth to the stomach through a movement called peristalsis. The epiglottis in the back of the throat prevents food from going down the trachea airway instead.
Inside the stomach, digestive juices break the food down even further. A sphincter from the esophagus to the stomach is responsible for keeping this digested food from coming back up the esophagus and being regurgitated. After the stomach breaks the food down, it moves into the small intestines.
The small intestines are made up of three parts - the duodenum, jejunum, and the ileum. As food passes through these three connected parts of the small intestines, the food mixes with more juices from the pancreas, the liver via the gallbladder, and the intestines while water and nutrients are absorbed. Waste products continue to move through the small intestines into the large intestines which are made up of four parts - the cecum, colon, rectum, and anal canal.
Finally, the cecum connects the ileum to the colon where stool is stored until the feces eventually leave the body through the rectum and anal canal.
How Long Does the Digestive Process Take in a Dog?
The entire digestive process, from the mouth to the anal canal, has historically been said to take about 6 to 8 hours in dogs, but some studies suggest that it is 13 hours.
It is thought that the digestive process for giant breed dogs could take considerably longer than for smaller dogs, even taking as long as 21.5 to over 57 hours.
These discrepancies show that this process can vary greatly depending on the size and breed of dog, health conditions, stress, type of food, and other factors.
The whole process should not be confused with how long it takes for food to move out of the stomach, though. People often think about digestion as how long it takes for a dog's stomach to be empty and this is not the same thing.
A dog's stomach may completely empty in as little as 1.5 hours but some studies suggest it is more likely between 4 and 10 hours or closer to the 6 to 8 hours that is commonly stated to be the digestion time of a dog. Again, this will depend on several factors, most importantly how much food and how liquid the food is.
Digestive Problems in Dogs
Some dogs will digest food more slowly, quickly, or less efficiently than others if they have a problem that affects their digestive system. Examples of these types of problems include:
- Foreign bodies
- Tumors in the digestive system
- Exocrine pancreatic insufficiency (EPI)
- Intestinal parasites
- Viral or bacterial infections in the digestive system
- Inflammatory bowel disease (IBD)
- Gastric dilatation volvulus (GDV)
- Trauma to the digestive system
- Liver disease
- Gallbladder disease
These and other problems can result in a lack of digestive juices and enzymes needed to break down food, increased or decreased motility of peristalsis which can lead to not absorbing nutrients properly or constipation, regurgitation of food, blockages that prevent food from traveling through the digestive system, and more.
Reich, C., Salcedo, M., Koenigshof, A., Hopp, M., Walker, J., Schildt, J. and Beal, M. Retrospective evaluation of the clinical course and outcome following grape or raisin ingestion in dogs (2005–2014): 139 cases. Journal of Veterinary Emergency and Critical Care, 30(1), pp.60-65. 2019. doi:10.1111/vec.12905