Water intake is important for maintenance of normal body processes. In general, horses should be allowed free access to fresh, palatable water. Ideally, daily water intake should be monitored so variation in intake levels are noted, and related to the general health status of the horse. This monitoring is difficult when using automatic watering devices, when housing horses in groups or when water is available from natural sites such as lakes, ponds and flowing sources.
A sudden shift to extremely cold weather may reduce water intake by as much as 14%. The practical significance of variations in water intake during cold weather is questionable, and most likely influenced by feed intakes, individual variation in horses, and length and degree of the temperature change. On one hand, horses have long survived in natural environments with frequent temperature changes. On the other hand, water restriction has been implicated as a contributing factor to colic, and several health professionals have noted increases in colic at times of major weather shifts. Although the old adage of 'you can lead a horse to water but you can't make him drink', is quite true, there are management routines that can be implemented to assess intake, and encourage it as much as possible.
Horses housed in barns should be expected to maintain more a uniform intake of water as compared to those housed 'outside' where temperature variations are larger. If there is a noted preference, horses may prefer drinking from buckets or other sources with a significant depth of water such as float tanks. The probability and significance of this preference will largely depend on individual horse behavior and contributing management practices. The biggest advantage to buckets is water intake can be monitored. The disadvantage is the need for manual refilling, and in cold weather water will freeze quickly.
Although different trials have varying results, lukewarm water is usually preferred over ice water. Again, the general significance of this temperature effect is difficult to assess because of all the variations between horses, weather differences and management. Heated sources of water are essential if the only alternative is ice, so when extreme, freezing weather is expected to last for more than a day, water heaters may be needed. Of course, water heaters are not without potential problems as they are electric, and to avoid risk, horse access to electrical cords and heating elements should be avoided. Alternatives to heating water sources include a variety of automatic, insulated waterers, most with an insulated water container and a flap or ball valve that a horse must push for water access.
Horses, when given the alternative, will usually drink several times per day, so having water sources near congregation areas may promote the frequency of drinking. Increases in intake of feed also increases the desire for water, so access to high fiber feeds such as hay when pasture is unavailable has added benefits over supplying a safe, continual supply of feed nutrients.
The bottom line is that horses need access to water, and the most recommended way to supply water is a continual, free choice method of drinkable water. Monitoring level of intake is preferred and practical in most individual housing situations. When concerned with water intake, ensure a palatable supply of fluid water, locate the water source in proximity to natural congregation areas, and promote intake by supplying forage supplementation in the same general area of the water source.
The need to increase management, above those suggestions, such as supplying a heated source, or moving horses out of weather extremes to enhance water intake, is difficult to universally state. The effect of other management practices, individual differences in horses and the variations in weather are influencing factors that have to be considered. However, farms with repeatable history of colic during times of sudden decrease or low temperatures should assess how water is being supplied, and consider altering management to enhance water intake during cold weather.