Lots of Fresh Water
A horse's make-up is about seventy percent water. She must always have fresh water available to her, whether in her stall or in the paddock or pasture. If dehydrated only to a factor of twenty percent (about two to three days), she could die. Water aids in cleansing the horse's body of toxins, lubricates and aids the digestive process, which helps to avoid impaction colic, and helps to distribute nutrients throughout the body.
Body weight, body type, breed, workload, and weather can be determining factors in how much a horse will drink—but not necessarily. Generally speaking, a normal size horse will drink about seven to ten gallons of water per day. A hardworking horse might lose four to five gallons of sweat a day and require twice the amount of water as the average nonworking horse.
Although she is not exercising, a lactating mare will require significantly more water than a relatively idle horse of the same type. She is producing milk to feed a foal and requires a disproportionately high amount of water to body weight.
A bigger horse does not necessarily drink more water than one that is smaller. Fat and muscle mass are factors in water consumption, but every horse is an individual and will probably find his own balance. However, a 2,000-pound draft horse must maintain his approximately 1,500 pounds of water mass, and so he will probably drink more than a 700-pound thoroughbred involved in a similar work regime.
Some horses indigenous to or developed in hot or arid climates like the Arabian will sweat less and have adapted to a lesser water requirement than other types of horses. Otherwise, there is no definitive water requirement according to breed.
Horses will require less and drink less water in colder weather. Sometimes, they are more apt to dehydrate in cold weather because they are often worked less and feel less inclined to drink. Also, very cold water is not agreeable to a horse and might prevent some horses from drinking. A salt block in the stall or paddock will generate thirst and is a good idea for winter as well as summer.
A horse that is “hot” during or after work should not be allowed free access to water. He could cramp up or even develop colic. However, short drinks, about three seconds long every once in a while, will help him stay hydrated and healthy during a workout.
What do I do if my horse is not sick but refuses to drink?Horses might reject water from a different source than they are used to. “Flavoring” their current water with peppermint oil or molasses, and their new source with the same, might help them acclimate.
Very cold water should be heated up with heating elements in buckets or water troughs to around 40 degrees. This will encourage a horse to drink, as well as make it less taxing on his body temperature during the colder months. If heating is not a possibility, water buckets or troughs should be changed out with fresh water a couple times a day. Water coming from a ground source will be between 35–45 degrees in the wintertime.
For pasture kept horses that get their water from natural sources on the property, it is important to have the water tested for potability (whether or not it is safe to drink). You never know what is going in the water upstream from you. Also, this source must be checked regularly in both very cold and very hot temperatures to make sure it isn't inaccessible because of freezing, drought, or obstructions up stream.