Impaction colic can happen during the winter months when horses or ponies are fed hay and have only frigid water to drink. The combination of dry feed and dehydration can be disastrous. Because the horses don't drink enough water the food forms an obstruction in the intestine. A horse that eats its bedding or accidentally gorges on grain can suffer from impaction colic. (Over eating grain or fruit can also cause laminitis or 'founder'.)
Parasite damage or kidney stones may also cause colic symptoms. Colic can be caused by too much food eaten too quickly, or drinking a large amount of cold water. But any horse, regardless of age or temperament can have a bout of colic and often the root cause goes undiscovered.
Twisted intestines and telescoped sections of intestines occur and the cause is unclear.