Dehydration: The #1 Winter Colic Trigger - How to Prevent It

By Juliet M. Getty, Ph.D.

Winter brings its own set of challenges to horse management, but none is as consistently underestimated—or as potentially dangerous—as dehydration. While most horse owners associate impaction colic with sudden weather swings or poor-quality hay, the truth is far simpler: horses drink less when it’s cold, and this natural decline in water intake remains the most common cause of winter colic.

Understanding why this happens and implementing a few key management strategies can dramatically reduce the risk.

Why Horses Drink Less in Cold Weather

As temperatures drop, a horse’s natural thirst mechanism weakens. Unlike summer—when the body works hard to cool itself—winter provides far less physiological stimulus to drink. But an even more important physiological shift occurs.

Cold weather reduces antidiuretic hormone (ADH), which increases urination and leads to the loss of free water. This initially raises blood sodium concentration, but the cold simultaneously blunts the thirst response. Because vasoconstriction keeps more blood in the core, the body misinterprets this as adequate hydration, sending weaker signals to the hypothalamus—the brain’s thirst center.

As a result, horses fail to drink enough to replace water losses. Over time, the body compensates by shifting internal water into the bloodstream, which lowers sodium concentration and suppresses thirst even further.

The outcome? Many horses quietly drift toward dehydration long before any outward signs appear. And because winter diets are heavily forage-based—requiring substantial water for digestion—the risk of impaction colic rises sharply.

Proven Strategies to Encourage Winter Drinking

Helping horses maintain adequate hydration requires a combination of temperature control, palatability, and consistency. These practical, barn-tested methods make the biggest difference:

1. Keep Water Warm

Horses drink most readily when their water is kept between 45°F and 55°F. Heated buckets, trough heaters, and thermostatically controlled systems can make an enormous difference in maintaining this range. Even if you’re fortunate enough to have an insulated barn, it’s still important to check water temperature daily, as conditions can shift quickly in winter.

2. Provide Salt Daily

Salt is the simplest and most reliable way to stimulate a horse’s natural thirst. A full-sized horse needs one ounce (2 tablespoons) of plain salt per day, regardless of the season. This should ideally be divided between meals since most horses do not enjoy meals that are too salty.

Salt blocks and rocks should also be readily available for additional salt requirements.  

One important caution: never add salt directly to a horse’s water. Doing so may cause them to refuse the bucket entirely, putting them at increased risk of dehydration.

3. Adding Electrolytes in Winter: When They Truly Help

Electrolytes can be helpful for athletes during cold weather, but only when used appropriately. Always start with salt first, as this is the foundation of proper hydration. Electrolytes are most helpful for horses who sweat during winter exercise because their primary purpose is to replace perspiration losses.

You can offer electrolyte water alongside plain water—never as a salt replacement—or simply top-dress electrolytes onto a meal. Whichever method you choose, remember that electrolytes are meant to supplement, not substitute for, the daily salt requirement.

4. Make Water Appealing

If your horse is drinking from an unfamiliar water source -- such as when traveling -- you may need to encourage water intake by adding a familiar flavor. A few helpful options include:

  • A splash of unsweetened apple juice
  • A handful of soaked hay cubes
  • A small amount of beet pulp “tea”

And be sure to keep buckets and tanks clean.  Algae isn’t just a summer problem.

Recognizing Early Signs of Dehydration

Winter dehydration can be subtle, so it’s important to watch for small changes. Signs may include dry, firm manure balls, tacky or sticky gums, a capillary refill time longer than two seconds, lethargy or a reluctance to eat hay, and reduced or darker urine output. Your daily, hands-on observation is the best early-warning system you have.

Adding Moisture to Winter Diets

Hay intake naturally increases in winter because horses rely on forage fermentation to generate internal warmth. However, digesting all that extra hay requires a significant amount of water. One of the easiest ways to support hydration is to add moisture directly to your horse’s meals.

Soaked hay pellets or cubes, soaked beet pulp, or even lightly dampened hay (not dripping -- just gently moistened) can all make a meaningful difference in overall water intake.

Be careful with weekly mashes. Wheat bran can irritate the gastrointestinal lining and tends to promote loose manure. Choose rice bran, instead. But, traditional “bran mashes,” offered only occasionally, may do more harm than good by disrupting the microbiome and increasing colic risk. If you choose to give a rice bran mash, offer it daily so the bacterial population in the hind gut can adapt.

Managing Ice: High-Tech and Low-Tech Approaches

When you have access to power, managing ice is much easier. Heated buckets, trough heaters, and thermostat-controlled tank systems can keep water at drinkable temperatures with minimal effort. Just be sure that all outdoor-rated cords, plugs, and outlets are routinely checked for safety.

Without power, the focus shifts to two key principles: agitation and insulation. Agitation prevents a solid ice sheet from forming, while insulation slows the freezing process. Practical low-tech options include wrapping troughs with insulation, using large floating balls to disturb the water surface, placing black rubber buckets in sunny areas, or partially burying tanks below ground level so the earth helps keep them warmer. Adding warm water several times during the day and night may be necessary to help keep water accessible.

It’s worth noting that metal troughs freeze rapidly, while plastic or rubber containers tend to freeze more slowly and are often more practical in cold climates.

Common Ice-Breaking Mistakes to Avoid

  • Do not hit troughs with a hammer — metal and plastic crack easily.
    Instead, use a rubber mallet or tools designed for ice removal.
  • Do not add salt to troughs — it won’t melt ice safely and discourages drinking, as described earlier.
  • Do not rely on once-daily checks — water inspection must be done continuously every few hours, even during the night.

How Steady Water Intake Helps Prevent Colic

A horse’s digestive system depends heavily on water. When water intake drops, saliva production decreases, chewing becomes less efficient, and intestinal motility begins to slow. The digestive tract muscles also struggle to move fibrous material along properly. Together, these changes dramatically increase the risk of impaction colic.

Consistent access to clean, drinkable water—paired with high-quality forage—is one of the most powerful tools we have for preventing winter colic and keeping the digestive tract functioning as it should.

Bottom Line

Winter dehydration sneaks up slowly—but it is entirely preventable. Warm water, daily salt, added moisture in the diet, and clean, accessible water sources create a powerful foundation for cold-weather health. When you give water the same priority as forage and shelter, you can dramatically reduce the risk of dehydration-related colic all winter long.

 

For Permission to Reprint

For permission to reprint this article, in part or in its entirety, please contact Dr. Juliet Getty directly at Gettyequinenutrition@gmail.com.