Winter colic in horses isn’t an unfounded fear. When asked to describe the most common wintertime equine health problem in their areas, veterinarians and horse owners around the country respond with near unanimity: Colic. Even in the Southwest, where frigid temperatures are extremely rare, cases of impaction and sand colic spike during the winter months.

Three cold-weather practices converge to increase the likelihood of intestinal blockages (impactions) this time of year:

• Horses tend to consume less water in colder weather, either because they don’t get as thirsty as in the summer or because their water sources freeze over. In addition, the roughages common in winter rations contain less than 20 percent moisture compared to the 75 percent or more water content in spring and summer grass. With insufficient liquid in the digestive tract, the food being processed becomes too dry to be moved along by peristaltic action and blocks a portion of an intestine. The stemminess of poor-quality hay contributes further to blockage formation.
• When the temperature drops, caretakers are inclined to boost their horses’ grain rations to meet the increased energy demands of keeping warm. This disproportion of carbohydrates to fiber can upset digestion.
• The digestive system depends on body movement to help push food along. At pasture, a horse spends the bulk of his time wandering from one grazing spot to the next. The inactivity enforced by confinement in stalls or small paddocks may slow the movement of ingesta along the digestive tract.When one or more of these influences produce an impaction, a course of intravenous fluids may be all it takes to soften the blockage and cure the colic, in which case the prognosis for long-term survival is excellent. If the blockage persists and requires surgery, the survival rate is greatly diminished.

Cold weather may conspire against your efforts to keep water flowing to your horses, but they are crucial to preventing colic. “We have gotten many of our clients to give their horses warm water and electrolytes [in their feed] during cold spells,” says Jeffrey Witwer, VMD, of Camden, South Carolina. “Anything that can be done to keep the horses drinking reduces the incidence of colic.” Your particular “anything” may be purchasing water-trough or -bucket heaters, carrying hot water to thaw frozen buckets and pipes or trekking twice daily to the stream to break a hole in the ice and check on the footing.

Leave your horses turned out as much as possible to ensure sufficient digestive stimulation. You won’t be endangering their health in other ways, as horses in good condition with heavy winter coats or adequate blankets and access to windbreaks can withstand temperatures as low as 40 degrees below zero. Unless they are being pelted by drenching rain or stinging ice, they are better off outdoors.

Finally, reach for an extra flake, not scoop, when temperatures start to drop: It’s hay, rather than grain, that provides the most efficient heating fuel. And roughages don’t produce the carbohydrate overload that can trigger endotoxemia, a system-wide toxicity that’s reflected in colic and/or laminitis.