DEAR DR. WELDY’S: I have noticed with the colder weather that my horse does not want to drink as much water as she usually does. She seems to eat well and is acting normally. How much water should she be drinking and is it a problem if she doesn’t?
DEAR READER: It is not unusual for livestock to drink less water in the winter than in the warmer months. Their water requirements are somewhat less when the temperatures drop due to decreased loss from sweating, but they should still be drinking an average of 5 gallons of water a day. This amount can vary between individual horses, so get to know how much your horse might consume on a mild day. This can serve as a yardstick to compare to when the weather gets cold.
If your mare is drinking significantly less water each day, yet is ingesting the same amount of hay and grain, eventually impaction colic can develop. With less moisture in the intestinal tract, feed material moves through the body at a slower rate. The horse’s body continually absorbs additional water from the intestine to maintain hydration. Eventually, the fecal mass becomes so dry and large that it clogs up the system, not allowing anything to pass. In the horse, this typically occurs in the large intestine because the length of this organ is such that it must be folded up inside the abdomen in order to fit.
This folding produces bends in the large colon that makes it more difficult for feed material or ingesta to pass through. At two of these bends — the “pelvic flexure” and the “right dorsal colon” — there is a reduction in the bowel diameter making the problem even worse. Still this digestive system works very well when the horse is allowed to walk and graze grass for 18 hours a day. Put that same horse in a stall with relatively little turnout, decreased water consumption, and feed her dry hay in two feedings for weeks to months. Now you have the potential for problems.