A recent study from England helps explain why moving horses from full turnout to stall confinement seems to increase their risk of colic.
Researchers at the University of Nottingham followed seven horses as they made the transition from living at liberty on pasture to being housed in stalls and exercised on a regular schedule. This design mimicked the common practice of returning horses to work after a rest period, which “is associated with large intestinal impactions,” says Sarah Freeman, BVetMed, PhD, who supervised doctoral student Sarah Williams in conducting the study.
The horses were first monitored when they were on full turnout, eating only grass and undergoing no structured exercise. For data collection, researchers placed the horses in individual paddocks for 24-hour periods twice during a weeklong study. In the paddocks, each horse’s water intake and manure output was tracked and the collected feces analyzed for moisture content. The researchers also used ultrasonography to measure the motility (activity) of the horse’s gastrointestinal system. “Ultrasound is used to look at the movement of the intestinal wall and count the number of intestinal contractions,” says Freeman. “The number of contractions are reduced for various colic conditions, including impactions and strangulations.”
The horses were then moved into stalls, switched to a diet of grass hay and exercised twice a day. The researchers monitored the horses for 14 days after the transition, collecting the same data on water intake, manure output and composition, and gut motility.
The data showed that the horses drank significantly more water when stabled, but they still had drier manure. On average, the horses on pasture drank 12 liters of water (slightly more than three gallons) per day and excreted 18.8 liters (almost five gallons) of water daily in their manure. In contrast, when stabled, the horses drank an average 32 liters (just under 8.5 gallons) per day and their manure contained only 6.6 liters (about 1.7 gallons) of water.
Noting that the latter change is due to both a decrease in the amount of feces produced and a decrease in water content of manure, Freeman says, “My opinion is that they are drinking more to compensate for the drier diet while stabled, compared to the [pasture] grass. But even this big increase is not enough to compensate for the difference in the dry matter content of the diet. I think this is the really interesting aspect of the study: They are trying to adapt, but the differences in diet are so much that they can’t.”
The researchers also discovered that each horse’s gut motility slowed significantly in the first five days after the transition from pasture to stable. “There are probably a number of factors that account for the change in motility,” says Freeman. “We change so many things by moving them from pasture to stabling. A number of these have been shown to affect motility. [For instance] chewing and the presence of food in the stomach and intestine stimulate motility, so a continuous intake of food is more likely to establish a steady, regular rhythm of motility.”
Although none of the study horses developed colic, the two who showed the greatest physiological changes after the transition did have a history of colic.
Freeman says that this study underscores the importance of making management changes, even in stabling, very gradually. “It is difficult for a lot of people, but in my opinion, the ideal would be to have a crossover period, with some time at pasture and some time stabled, rather than an abrupt transition,” she says. “If owners can’t do a gradual transition---for instance, a horse who has to be brought in and stabled suddenly for an injury---then knowing that the critical period is the first five days may help them monitor the horse carefully and therefore pick up any signs early.”
Reference: “Water intake, faecal output and intestinal motility in horses moved from pasture to a stabled management regime with controlled exercise,” Equine Veterinary Journal, February 2014
This article first appeared in EQUUS issue #440.