Snow is not sufficient as a water source.

The colored urine that some horse owners find in their horse's pasture is from plant and bile pigments. It’s excessively dark because the urine is concentrated.  The horse isn’t taking in enough water.

Dehydration in winter is a real threat. Loss of fluids in sweat obviously is greatly decreased, but loss of water through the respiratory tract when breathing dry winter air increases. Most importantly, the horse still needs to secrete large volumes of fluid into the digestive tract and make urine.

Most owners increase the amount of fibrous feeds fed in the winter, to help warm the horse from the inside out by the heat of fermentation, but high-fiber feeds require high intakes of water, 1 to 2 quarts for every pound of dry matter, which means 5 to 10 gallons for a horse with a hay intake of 20 pounds.

Darkly pigmented urine is your first clue that the horse’s water intake is marginal. Left uncorrected, dehydration, colic and impaction are just around the corner.

Some strategies to increase your horse’s water consumption are:
• Add table salt (iodized is fine) directly to the horse’s meals, a minimum of 1 oz./day divided between feedings. The salt will increase his desire to drink. Two tablespoons of salt equal one ounce.
• Incorporate warm, soupy mashes into the diet.

You can make these at home and take them to the barn in an insulated container. You can make up several ahead of time, store in the refrigerator, and then heat in a microwave before use.
• Invest in insulated or heated water buckets.
• Frequently break the ice in your horse’s water tank during cold weather, when he’s turned out.
• Make watering your last chore. The horse is more likely to drink well after it has been eating for a while.
• Don’t skimp on dumping and cleaning buckets.
• If you have hot water available, water with warm water. This can make a huge difference in how much water the horse consumes. If you don’t have hot water at the barn, consider bringing a gallon of hot water with you in a drink cooler, to add to your horse’s bucket. However, you can’t do warm water one day and not the next. Consistency will be key here, as your horse will become even less likely to drink cold water if he’s hoping there might be a drink of warmed water coming some time in the future.