There are many ingredients that go into a quality dog food, and here we will focus on just one category: the carbohydrates. Carbohydrates typically make up anywhere from 30-70 percent of a dry dog food. They come mainly from plants and grains, and provide energy in the form of sugars.Carbohydrates have several important functions in a dog food.here are many ingredients that go into a quality dog food, and here we will focus on just one category: the carbohydrates. Carbohydrates typically make up anywhere from 30-70 percent of a dry dog food. They come mainly from plants and grains, and provide energy in the form of sugars.