Like all living organisms, horses need to take the materials to build or repair tissues or cells and produce energy. The nutrients in the horse's natural diet are mostly supplied from the grass. The herb is a plant and, as all plants are able to absorb simple substances like water, carbon dioxide and nitrogen and inorganic minerals and convert them into more complex organic substances such as carbohydrates and proteins. Green plants are able to convert the energy of sunlight into chemical compounds to produce organic complexes. These organic substances produced by plants then provide nutrients to the animals that graze grazing. The plants produce carbohydrates from carbon dioxide and water through the energy of sunlight. This process is called photosynthesis, It occurs in the leaves of all green plants, and then the leaves are to be considered as carbohydrate factories. Like all other animals, horses have a limited ability to produce the carbohydrates they need, being herbivores, eat vegetables, especially grass with a high fogliarità. All that horses eat and drink every day is to form the animal's diet and a diet that contains all the nutrients in the correct proportions is defined as "balanced". The ration is the amount of food provided to the horse in a day, which must be designed according to the type dell'equide and possibly work done.

(taken in some passages from the book by Zoe Davies – The Equine Supply – Italian translation by Marcello Hinxman Allegri and Giuseppe Iardella, ed. Raffaello Cortina)