Carbohydrates are the most abundant biomolecules in nature, having both structural and energy reserve functions. The feeding of ruminant animals is based on the use of fodder which contains fibrous carbohydrates (hemicellulose, cellulose and lignin). Due to their high energy content, carbohydrates are the main energy suppliers for mammals. Ruminants have developed a symbiotic relationship with microorganisms, which has given them the ability to use fibrous carbohydrates as a source of energy, both for maintenance and to generate animal products.