The improvements in horse health care over the last 20 years have been amazing. Unfortunately, colic continues to be the No. 1 non-infectious killer of horses. And impaction colic of the large intestine is the most common form of?colic encountered during the cold winter months.
We all know that sudden changes in a horse's activity level, diet and stabling increase the risk for colic. Horsemen and veterinarians have long observed that horses kept on pasture colic less than those spending most of their time in stalls. Now, research from the University of Nottingham in England suggests that changes in intestinal motility may account for that decrease.
In the study, researchers selected 16 horses and divided them into two groups. The first group of eight (Group A) was kept in stalls bedded with shavings for two weeks and turned out each day for 60-90 minutes of free exercise. They had continuous access to fresh water and were fed hay and grain twice a day. The second group of eight (Group B) was kept on grass pasture 24 hours a day, with continuous access to fresh water. They received no grain or forced exercise.
After two weeks, the groups were switched, with Group B being placed in stalls and Group A turned out to pasture for an additional two weeks following a gradual introduction period to their new surroundings and feed.
During the study, each horse's intestinal motility was measured twice daily using ultrasound to chart the number of gastrointestinal contractions. Keep in mind that intestinal contractions are how the horse moves feed through its intestinal tract to digest it.
When the study was completed, it was found that intestinal motility was significantly lower in stabled horses than in those kept on pasture. Slower motility means that food is retained longer; therefore, the intestinal contents become drier. This was especially true in the pelvic flexure, where the horse's colon narrows and turns back on itself. This portion of the intestinal tract is the most common site of colon impaction due to dry intestinal contents, which are a major cause of colic during the winter months when horses are not drinking enough water.
Of course, the study did not determine why there was decreased intestinal motility in stalled horses and a greater probability for impaction colic. That will have to be determined in future studies. Since neither group was fed a large amount of food or subjected to hard work, it seems logical to me that water intake, either through drinking or grazing, as well as regular low-level exercise seems to support normal intestinal motility and a decreased incidence of colic.
Future research will be aimed at determining the factors that are the most important. Until that research is done, we should try to mimic a horse's natural lifestyle by providing a high percentage of grass or hay in their diet, low levels of grain, small meals several times a day and as much free exercise as possible. Horses are designed to spend 16-20 hours a day grazing and consuming small amounts of roughage. We should emulate that natural behavior as much as possible.