I mention the importance of adequate water intake in winter so often I’m sure some people are sick of hearing it, but it’s such an important and widespread issue that it merits being repeated.
The horse’s body is estimated to be 60 to 68+% water in adults and up to 80% water in young, growing animals. It is found in all tissue types and is the base component of blood, urine, bile, semen and all body fluids. Water is essential for digestion, beginning with the secretion of saliva, and needed for nutrient absorption and entry into cells. Metabolic reactions require water. For example, 7 grams of water is needed to produce just one gram of glycogen, the storage form of glucose in muscle cells and liver. Water cools the body via sweat production and evaporation of water from the lungs.
Dehydration can kill the horse much quicker than not eating, but many things happen first. Even a slightly dehydrated horse has an obviously decreased exercise tolerance and endurance. Digestive impairment occurs, often leading to colic from impaction and/or electrolyte disturbances. If dehydration progresses, shock from falling blood pressure and organ failure results.
Horses can survive, at least for a while, by eating snow when water sources are frozen but this is not going to result in optimal water intake. Domesticated horses in particular are at very high risk of colic and impaction because their winter diet is dried (even dormant grasses contain water) and they don’t move around as much as feral horses.
Electrical deicers prevent water from freezing but do not warm it. To make water comfortably warm, which is what horses prefer, you need a water heater. Since horses are much more likely to investigate and chew on cords, this is far riskier with horses than other types of livestock.
The ideal is to provide warm water for drinking at least twice a day. Insulating buckets and tubs will keep the water warm for longer periods. If there is no hot water at the facility, you can heat it with a water heater while there (this can take quite a while in cold weather), or bring hot/boiled water with you in a large thermos if a single horse or inside large picnic coolers for more horses. Once the horses discover they are getting warmed water you will find they drink long and well immediately.
Finally, remember not to let up on salt supplementation. For a 1000 pound horse, provide at least 1 ounce of loose salt per day, in meals or sprayed as a solution on the hay. Salt is required to hold water in the tissues and provide the drive to drink.
The extra effort to give warmed water will pay off if you avoid even one case of impaction.
Eleanor Kellon, VMD