Your question is not fully clear,i tried my best to give answer if you are expecting different answer than repost the question with proper clearity in the question.
Digestion is the process of breaking down feed into simple substances that can be absorbed by the body. Absorption is the taking of the digested parts of the feed into the bloodstream. The digestive system consists of the parts of the body involved in chewing and digesting feed. This system also moves the digested feed through the animal’s body and absorbs the products of digestion. Different species of animals are better able to digest certain types of feeds than others. This difference occurs because of the various types of digestive systems found in animals. There are four basic types of digestive systems: monogastric, avian, ruminant, and pseudo-ruminant.
Different animal will eat different type of food and that's why they have different type of digestive system
There are so many factor which will affect the type of food we are taking
Go through the link i mentioned belo to know about factors