How much water does your horse need to drink every day to stay healthy and how much do water requirements increase in hot conditions or when working?

Ensuring adequate water intake is important for the optimal health and well-being of all horses. Some horses are more susceptible to becoming dehydrated and have a higher need for water.

A typical, idle 500 kg horse requires at least 25 litres (6.6 US gallons) of water per day.

In hot weather, horses may require 55 litres (15 US gallons) per day and they may need anywhere from 40 – 70 litres (10 – 18 gallons) per day when exercising.

Even if you provide your horse with constant access to fresh clean water, horses will not always drink enough water to avoid dehydration.

In particular, water intake should be intentionally encouraged in exercising horses, lactating mares, horses with gastrointestinal issues, and during both hot and cold weather.

This article discusses why adequate water intake is important, factors that can affect water intake, how to assess dehydration, and how to encourage water consumption in horses.

Importance of Water Intake for Horses

Water is one of the most important nutrients your horse requires in its diet. Water is indirectly involved in all physiological processes essential for life.

This includes biochemical reactions that take place within the body, as well as the ability to maintain and regulate the body’s internal temperature.

The average adult horse’s body is composed of approximately 70% water. [3][4] This water is distributed within the cells of the horse’s body, in blood, as well as within organs that contain fluid, such as the stomach and the bladder.

Inadequate water consumption can negatively impact your horse’s health for a number of reasons and can contribute to diminished exercise performance and impaired cognitive function.

Common signs of dehydration include sunken eyes, general dullness and loss of skin elasticity. Prolonged dehydration can lead to more severe outcomes, such as impaction colic and even death in extreme cases.

Horses experiencing gastrointestinal issues such as diarrhea should be closely monitored for signs of dehydration due to excess fluid loss.

Performance horses also need their water intake closely monitored. Performance horses have a high water requirement because of their exercise demands, variations in husbandry, and potential exposure to hot and humid environments.

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Water Requirements

Water requirements for horses vary depending on age, digestive health, diet composition, body condition, activity level, and perspiration rates.

Horses on pasture obtain more water from their forage and require less drinking water. Conversely, horses consuming hay and grain will need to drink more water to replenish hydration status.

The estimated water requirement for a horse at maintenance consuming hay is approximately 50 – 60 mL/kg body weight daily.

For the average 500 kg horse, this is 25 – 30 L (6.6 – 8 US gallons) of water per day. [1][2]

Below are general guidelines to consider:

Physiological State Water intake (L) Reference
Maintenance (Moderate Climate) 7 L per 100 kg BW [14]
Maintenance (Hot Climate) 12 L per 100 kg BW [14]
1 Hour Post-Exercise 12 – 28 L [24]
Moderate to Heavy Exercise up to 90 L per day [16]
Lactation up to 75 L per day [16]


These are estimates of intake based on available studies. The values above do not indicate the amount of water that should be provided to the horse.

Horses should always have free access to unlimited water wherever possible.

Careful formulation of the diet can also be beneficial for supporting water intake, particularly in moderate to very heavy exercising horses and lactating mares.

You can submit your horse’s diet for evaluation by our equine nutritionists to develop strategies to support adequate fluid intake.

Hydration Status

Horses that are regularly exercised and competing at a high level, lactating, and/or travelling are at an increased risk of becoming dehydrated.

Dehydration occurs when the amount of water lost through feces, urine, sweat, and respiration is greater than the amount consumed through feed and water consumption.

Mild dehydration occurs when there is a loss of 5% of total body water. For the average 500 kg horse, this would be approximately 18 L of water. [5]

Mild dehydration can negatively impact performance, impair mental focus and cause the horse to tire more quickly.

A water loss of greater than 15% total body water can be fatal to the horse. [5] This is equivalent to a loss of 95 L of water for an average 500 kg horse.

Electrolyte Balance

Inadequate water intake can throw off electrolyte balance in the blood and within cells.

Electrolytes are essential minerals including such as potassium, calcium and magnesium that play a role in proper muscle contraction and nerve function. [6]

Horses with low electrolyte levels may experience the following symptoms: [6]

  • Fatigue
  • Muscle cramps and spasms
  • Tying up
  • Rapid heart beat
  • Low blood pressure
  • Neurological issues

Gut Health

Water intake is important to support gut health and digestive function. Horses that do not consume enough water are at greater risk for impaction colic and constipation.

The gastrointestinal tract functions as a reservoir for water during periods of exercise and when water is temporarily not available. [7]

If your horse does not have access to water for long periods of time, ingested food does not move through the intestines as quickly as it otherwise would. This is referred to as impaired gastrointestinal motility.

Research has found that a decrease in water consumption was the most commonly observed factor in horses preceding an episode of colic. [8] This is one of the reasons why sudden weather changes which affect water consumption can lead to adverse gastrointestinal conditions, including impaction colic.

Not drinking enough water can also contribute to gastric ulcers in horses. [9] The absence of water in the paddock has been identified as a factor that may increase the risk of ulcers.

Milk Production

Mares that are lactating require more water to support milk production. Lactating mares will increase their water consumption by 37 – 74% to ensure adequate hydration status. [5]

Mares that do not drink enough water may produce a lower volume of milk They may also produce milk that is of lower nutritional quality for the foal. [10]

Assessing Dehydration in Your Horse

There are a number of ways to evaluate whether your horse is dehydrated including: [11][12]

  1. Monitoring the volume of water consumed
  2. Mucous membrane moisture, color, and capillary refill time (CRT)
  3. Manure consistency
  4. Skin pinch test
  5. Visual assessment (sunken eyes, dull appearance and/or drawn up flanks)
  6. Bloodwork

The best and most reliable method to assess adequate water consumption and hydration by the horse is to measure the volume of water consumed. [13]

This can be done manually by counting how many buckets of water the horse has consumed or by connecting the horse’s automatic watering bowl to an individual meter.

Mucous Membranes and CRT

Evaluating your horse’s mucous membranes and capillary refill time (CRT) is an easy way to assess hydration status.

The easiest mucous membranes to assess are the gums – you simply lift your horse’s upper lip to visualize the gums. To evaluate CRT, you’ll take your finger and blanch the gum surface. The capillary refill time is the time it takes for the gum color to return to normal.