Hay fermentation is the process that leads to the creation of an environment that inhibits the growth of bacteria harmful to hay and is therefore crucial to guarantee its long conservation.
It is obtained by compacting the hay in the barn (to also reduce its size), so that less gas exchange occurs and thus the harmful aerobic microflora is inhibited, instead promoting lactic fermentation that ensures the good conservation of the forage.
If not correctly managed, fermentation leads to hay where sugars and amino acids react giving rise to molds that are indigestible and toxic to animals (and humans).
Furthermore, if not controlled correctly, fermentation, especially if the stored hay is too humid, can lead to spontaneous combustion (due to the increase in temperature of the hay caused by the activity of microorganisms).