How does hay help cows digestive system?

It is a roughage which does not break down as quickly or as easily as other feedstuffs do like alfalfa, grain, or green grass does. This way the digestion process is prolonged and prevents the animal from bloating because the feed isn't too rich. Hay will not help a cow's digestive system, however, if it is too poor-quality and coarse. A cow can easily die of a full stomach if hay is poor quality because it lacks any sufficient nutrients for a cow to live on. It'll just sit there and not do anything for her.