Rates of flow through the colon may take up to several days following eating. Because the diameter of different segments of the large colon varies and the arrangement includes several flexures where the colon turns back onto itself, horses are predisposed to digestive upsets when nutrient flow is abnormal. Because the horse's gastrointestinal tract is designed to digest primarily forage, fewer problems will occur when the diet is predominantly hay and pasture. The digestive system of the horse is susceptible to twisting, impaction and other types of colic. A natural response of a horse with a digestive disorder is to roll, which, in extreme situations, can cause a section of the intestine to become twisted.
Impaction can occur when a section of the intestine is damaged by parasites or toxins.
Colic results from the formation of gaseous products resulting from microbial digestion. Because these gaseous compounds cannot be absorbed or released as quickly as they are produced, gaseous swelling of the hindgut occurs. This swelling can, and often does, cause the horse to develop colic. Nutrient Requirements When fed properly, a horse's body is supplied with the energy, proteins, vitamins and minerals it needs and uses as it works. The harder the body must work and the more nutrients it uses means more nutrients must be supplied in the feed.