In Northern regions, grass is not permanently available (e.g. in rainy periods or periods of drought). Ensilage permits the farmer to have a sufficient storage supply of fodder to feed the animals available at the farm. Ensilage of maize is particularly interesting because it is rich in energy and provides a certain digestive comfort to the cows (in particular thanks to the presence of cellulose and to the maize starch properties). Furthermore, from an environmental perspective, maize has the advantage of often being cultivated on the farm itself which avoids the need for transportation.
Note: Evidence from paintings show that ensilage of maize was already used in the Nile valley between 1000 and 1500 BC.