But none of these is essential as long as we eat a balanced diet. But hay is an essential component in horse rations. Horses are forage consumers, eating forages as either pasture or hay. The horse's digestive system is unique among other farm animals. Cows and sheep are ruminants with a four-compartment stomach.
Swine are simple-stomached animals with a digestive system similar to humans.
The horse has a simple stomach like humans and swine but consumes forages like cattle. But humans and swine don't eat forage crops. The reason is their digestive system cannot digest the fiber in forages. The horse's digestive tract has a cecum and a large colon that holds considerable amounts of bulky forages. Microorganisms, living in the cecum and large colon, digest part of the fibrous materials that make up forages.