Those of us living on small hobby farms, or where pasture isn’t available for portion of the year will need to supplement our horse’s and pony’s diets with a bulky fodder. Hay fits this bill because its fibrous content and nutrition resembles the horse’s natural diet of grass. Missing is the moisture, which is why it is so important to always provide fresh drinking water.
The equine digestive system is very long, the stomach very small, and the digestive process relatively slow. To avoid constipation, which can be very painful,and other gastric problems, horses need large amounts of fiber. This is the reason why, although concentrated grain mixtures might provide adequate nutrition, they will not provide enough bulk. Slowly and constantly eating a high fiber feed helps keep the gut healthy and the digestive system functioning.
If you live in an area where the winters are cold, hay can help keep your horse warm. Digesting all that fibrous material generates a lot of heat. Having hay always available can also prevent stable vices such as cribbing and weaving, by providing an outlet for the horse’s natural foraging habits.