Dogs can eat large amounts of food at one time. In wild canines, this is called "gorging" and serves animals who hunt large game, giving them a chance to rest between hunts. A dog's teeth are designed to grip, tear and shred food, and its jaws are designed to open wide to take in large chunks of meat. The small teeth at the front of a dog's mouth are designed for scraping the meat off of bones. The canine teeth hold and tear the meat, the incisors cut and the molars grind. While humans chew their food, dogs do not. Digestion begins in your dogs' mouth when saliva lubricates the food before it goes directly from the dog's mouth into the esophagus (the tube that connects the mouth to the stomach).
When the dog swallows, the food passes through the esophagus and into the stomach. Food is broken down and mixed in the stomach before passing into the small intestines as chyme. The dog's stomach is very acidic, with a pH of 1 to 2, compared to the human stomach pH of 4 to 5. The high level of acid in a dog's stomach is what enables canines to eat meat and bones and not become ill from harmful bacteria.
Chyme passes into the small intestines where it gets additional digestion from enzymes added by the pancreas and liver. Carbohydrates and fats are digested, and nutrients are absorbed into the bloodstream. What is left then passes into the large intestines.
In the large intestines feces are formed and stored until the dog defecates. A dog's digestive tract is short compared to a human's digestive tract. Because of this, food passes through a dog's system quickly in comparison. From the time food enters a dog's mouth until the waste products are defecated from the body is generally between four to six hours for raw food and 10 to 12 hours for dry food. There are many factors that determine how quickly a dog digests food. Some dogs have more active bowels than others. Other factors include the type of diet, with foods with more fiber moving through your dog's system fastest. The amount of water a dog drinks also influences the time of digestion.