What are the manifestations of a dog's digestive characteristics?

In animal taxonomy, dogs belong to the order Carnivora. The ancestors of dogs mainly preyed on small animals, and occasionally filled their hunger with tuberous plants. After dogs were domesticated by humans, their feeding habits changed, becoming omnivores that mainly eat meat, but a vegetarian diet can also sustain life. Even so, they still retain a digestive characteristic of being mainly carnivorous. For example, a dog's teeth: the upper and lower jaws each have a pair of sharp canine teeth, reflecting the trait of carnivores being good at tearing at prey. A dog's molars are also relatively sharp and strong, able to cut food. When gnawing bones, the pressure between the upper and lower teeth can reach 165 kg, but they are not good at chewing. Therefore, when dogs eat, they really "wolf down" their food and rarely chew. A dog's esophageal wall has abundant striated muscle, and its vomiting center is well developed. After eating a toxic substance, it can trigger a strong vomiting reflex, expelling the toxic substance swallowed into the stomach, which is a relatively unique defensive ability. A dog's salivary glands are well developed and can secrete large amounts of saliva, moistening the mouth and feed, making chewing and swallowing easier. The saliva also contains lysozyme, which has a bactericidal effect. In hot seasons, it relies on the evaporation of water in saliva to dissipate heat, thereby regulating body temperature. Therefore, in summer we often see dogs opening their mouths wide and sticking out their long tongues precisely to replace sweating and dissipate heat. A dog's stomach is an irregular pear shape, and the hydrochloric acid content in gastric juice is 0.4~0.6%, ranking first among domestic livestock. Hydrochloric acid can cause proteins to swell and denature, making them easier to break down and digest. Therefore, dogs have a very strong ability to digest protein, which is the basis of their carnivorous habits. After eating, a dog can completely empty the food from its stomach in 5~7 hours, much faster than other herbivorous or omnivorous animals. A dog's intestinal tract is relatively short, generally only 3~4 times its body length, whereas the intestinal tracts of horses and rabbits, which also have a single stomach, are 12 times their body length. A dog's intestinal wall is thick and its absorptive capacity is strong; these are all typical carnivorous characteristics. A dog's liver is relatively large, equivalent to about 3% of body weight, and the bile it secretes is beneficial for fat absorption. A dog's defecation center is not well developed, and it cannot defecate while moving like other domestic livestock.

Dogs can digest and absorb protein and fat very well, but because they do not chew thoroughly and have short intestinal tracts, they do not have fermentation capacity, so their ability to digest crude fiber is poor. Therefore, when feeding dogs vegetables, they should be chopped and cooked, and it is not advisable to feed them in whole pieces or whole plants.