In the body of animals, carbohydrates, with the exception of a small amount of sugar and glycogen (a reserve fund of carbohydrates), are not deposited, but in exchange they are very important. Animal feeds are high in carbohydrates. In the digestive tract of an animal, carbohydrates under the influence of enzymes of saliva, pancreas and intestinal juices are broken down into water-soluble monosaccharides, mainly to glucose, absorbed in the small intestine, into the bloodstream, and then through the portal vein into the liver. Its cells retain glucose and synthesize glycogen. The rest of the glucose passes from the blood to the cells and tissues of the animal, where it is used for tissue nutrition with oxidation to carbon dioxide and water. The breakdown of carbohydrates is accompanied by the release of energy used by the body for muscle work. In the rumen of ruminants, part of the carbohydrates is broken down by microflora to lactic and volatile fatty acids (acetic, butyric, propionic) and absorbed by the body. Volatile fatty acids (especially acetic) in addition to the energy role also serve as precursors of milk fat.
With excess intake of the body, carbohydrates turn into fat, which is deposited in the cells of the connective tissue. With a lack of carbohydrates, the body spends other nutrients (proteins, fats), which is economically disadvantageous. At the same time, not only carbohydrate, but also protein and fat metabolism are disrupted. Carbohydrate metabolism is regulated by the central nervous system both by direct effects and through the endocrine glands.