Ruminants allow humans to take advantage of nutrient sources in certain plants that would otherwise not have any nutritive value for humans since the human stomach cannot digest them. Ruminants transform hay and several industrial by-products into very high-quality food: milk and meat.
In addition to field grass, cows feed on dry hay, grains and corn that are in grain form or stored moist, in addition to mineral salts, vitamins and silages. Silages are kept in airtight silos or wrapped in plastic to keep them moist while they undergo controlled fermentation. Most of these types of feed are produced on farms, which makes it possible to reduce the transportation of feed and avoid monoculture on farms.
In all animals, including humans, food must be transformed so that it can be absorbed by the blood and used by the body to provide it with the nutrients it needs. That is the role of the digestive system. In ruminants, such as cows, the digestive system is special because the stomach has four compartments: the rumen (paunch), reticulum (second stomach), omasum (fardel), and obomasum (true stomach). These four compartments, especially the rumen, give cows the ability to digest, transform and draw nutrition from more complex foods that are harder to digest, such as various forage plants (alfalfa, clover, millet and dactyle, to name just a few).
In one day, a cow eats over 20 kilograms of food and drinks around one hundred litres of water, which is the equivalent of a bath tub filled to the brim.