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 bodyâ€™s internal temperature.
The average adult horseâ€™s body is composed of approximately 70% water.  This water is distributed within the cells of the horseâ€™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.
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.
Below are general guidelines to consider:
|Physiological State||Water intake (L)||Reference|
|Maintenance (Moderate Climate)||7 L per 100 kg BW|||
|Maintenance (Hot Climate)||12 L per 100 kg BW|||
|1 Hour Post-Exercise||12 – 28 L|||
|Moderate to Heavy Exercise||up to 90 L per day|||
|Lactation||up to 75 L per day|||
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.
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. 
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.  This is equivalent to a loss of 95 L of water for an average 500 kg horse.
Inadequate water intake can throw off electrolyte balance in the blood and within cells.
Horses with low electrolyte levels may experience the following symptoms: 
- Muscle cramps and spasms
- Tying up
- Rapid heart beat
- Low blood pressure
- Neurological issues
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. 
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.  This is one of the reasons why sudden weather changes which affect water consumption can lead to adverse gastrointestinal conditions, including impaction colic.
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. 
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. 
Assessing Dehydration in Your Horse
- Monitoring the volume of water consumed
- Skin pinch test
- Capillary refill time
- Moisture in the mouth
- Fecal consistency
- Visual assessment (sunken eyes, dull appearance and/or drawn up flanks)
- Biochemical tests of the blood (total protein and electrolyte concentrations)
The best and most reliable method to assess adequate water consumption and hydration by the horse is to measure the volume of water consumed. 
This can be done manually by counting how many buckets of water the horse has consumed or by connecting the horseâ€™s automatic watering bowl to an individual meter.
Skin Pinch Test
The skin pinch test is another popular and easy way to evaluate hydration status. This test can be performed by pinching the skin to form a tent at the base of the neck and releasing it.
The skin should return to its normal position immediately. The longer it takes for the skin to return to normal, the higher the severity of dehydration.
If it takes 2 – 5 seconds for the skin to return to normal, this may indicate mild dehydration.
If it takes 10 – 15 seconds for the skin to return to normal, this may indicate severe dehydration. Veterinary attention may be warranted in this case.
However, this test is not the most reliable way to assess hydration status.
The time it takes for the skin to return to a normal position may also be affected by the site on the horseâ€™s body where the test is performed, the moisture level of the horseâ€™s coat, as well as the age of the horse. 
Factors that Affect Water Intake
The volume of water that a horse drinks is affected by a number of factors, including:
- Water content of the diet: Horses consuming dry feeds such as hay will drink more water than those grazing on pasture which has a higher moisture content (up to 60-80%) 
- Protein content of the diet: Excess protein in the diet results in excess nitrogen that needs to be excreted in urine which causes the horse to drink more water 
- Season: Ambient temperature and pasture consumption changes throughout the year both affect water intake 
- Water characteristics and availability: Water temperature, smell, taste as well as location and delivery method (bucket, trough or automatic drinker) can all affect intake 
- Exercise level: Exercising horses require more water than those at maintenance to replenish fluids lost in sweat 
- Size and body condition: Larger horses will require more water even under the same environmental and exercise conditions.  Overweight horses may require less water than a fit horse of the same weight because muscle contains more water than fat
- Breed: Breed differences may affect water intake
- Lifestage: Horses in lactation have a higher water requirement to support milk production 
These are all important factors to consider when trying to optimize water intake and delivery for your horse.
Tips for Encouraging Water Consumption
The following are eight simple and effective ways to encourage water consumption by your horse:
1) Increase your Horse’s Salt Intake
Salt intake is directly correlated with water consumption. Adding salt to a horseâ€™s feed will increase its water intake by stimulating thirst.
A study found that doubling the salt in feed from 50 mg/kg body weight to 100 mg/kg body weight increased water consumption by 53%. 
The average horse should receive at least one ounce (30 g / 2 tablespoons) of loose salt in their daily feed. Larger horses and horses undergoing moderate or heavy work should receive a higher quantity of loose salt.
Free choice, loose salt should also be provided to your horse at all times. Loose salt is preferable over salt blocks as horses simply cannot meet their sodium requirement from a salt block.
2) Provide Electrolyte Supplements
Providing your horse with salt and water is typically adequate to replenish fluid loss for most horses at maintenance or those in light recreational exercise.
However, for horses undergoing more intense and frequent exercise, supplementing electrolytes is recommended to replenish the electrolyte minerals lost in sweat.
Horses at maintenance may also require electrolytes when temperatures are very hot and humid or in other situations when it is necessary to encourage greater water intake.
One study found that horses that ran 60 km on a treadmill drank more water when an electrolyte was added to their water (24 – 26 L) compared to providing water alone (12.2 L). Water intake was slightly higher when the electrolyte contained added sugar. 
A good electrolyte supplement should provide the minerals lost in sweat (sodium, potassium, chloride) in the correct ratio. Electrolytes should also contain some sweetener and/or flavouring for taste. 
Electrolytes should be supplemented in water; however, they can be top-dressed onto feed or syringed as a paste if water is freely available.
Horses may require training in order to drink water flavoured with electrolytes. To help your horse adapt, slowly add an increasing quantity of electrolytes to their water over 1 to 2 weeks.
Mad Barnâ€™s Performance XL: Electrolytes supplement offers a convenient and effective way to re-establish electrolyte balance and prevent dehydration.
3) Provide warm water during cold weather
When outdoor temperatures are cold, it is important to provide your horse with room-temperature water to encourage hydration.
Research shows that in cold weather, horses will drink more warm water (~ 20Â°C or 68Â°F) compared to icy, cold water (0Â°C or 32Â°F). 
Exercising horses also drink more water or electrolyte solution when it is warm in temperature compared to cold. 
In warmer weather, water consumption is similar regardless of whether the water is warm or cold.
4) Ensure clean fresh water is always easily accessible
Water should be freely available and accessible to the horse when stabled and outside in the paddock.
Water troughs in the paddock should be located in a way that allows for the maximum number of horses to drink at one time.
Horses that have to walk further to access water will drink less compared to horses that have water freely available nearby. 
The water provided should be clean to minimize adverse tastes and smells that can discourage consumption. Common smells that may negatively impact water intake by the horse are: 
- Microbial by-products
- Rotting vegetation
Water buckets and automatic watering bowls should be cleaned on a daily basis. Automatic watering systems should also be checked daily to ensure that they are working properly.
Outdoor water troughs should be cleaned at least every couple of weeks to remove debris.
5) Use Light-Coloured Water Buckets
Automated watering systems provide horse owners with convenience; however, horses appear to prefer drinking out of a bucket versus an automatic watering bowl. 
Research shows that among horses adapted to both systems, horses drank more water from a bucket (24 L per day) as compared to an automatic system (17 L per day). 
The colour of the bucket can also impact water intake. Horses drink more from light-coloured buckets (turquoise, light blue and light green) compared to dark-coloured buckets (green, yellow and red). 
Water consumption is greatest with turquoise buckets. 
Of the automatic watering bowls available, horses appear to prefer those with a float valve compared to those with a pressure valve. They also appear to prefer larger bowls to smaller ones. 
Flow rate in automatic waterers can also affect the volume of water consumed by the horse. A study found that horses drank the most when water was refilled at a rate of 8 L / min, as compared to a slow rate (3 L / min) or a fast rate (16 L / min). 
6) Allow access to pasture
When horses are out grazing on pasture, a large percentage of their water requirement is met by the water they are consuming in the grass.
A horse on pasture will require significantly less drinking water than a horse on hay, grains or a complete feed.  These feeds contain a higher percentage of dry matter compared to pasture grasses.
When seasonally available, and depending on the condition and health of the horse, you can increase your horse’s water intake by giving them the opportunity to graze frequently.
Note that pasture access should be limited or avoided for horses that are over-conditioned, have metabolic concerns such as Equine Metabolic Syndrome or Cushing’s disease with insulin resistance, or are at risk of developing laminitis.
7) Soak or Steam Hay
Soaking or steaming your horse’s hay can help to increase water consumption by boosting the moisture content of the forage.  Soaking hay increases moisture levels by a factor of 5 while steaming increases levels by a factor of 2.
Soaking lowers the sugar content of hay which has additional benefits for horses that need to lose weight or those with metabolic issues.
However, it can also decrease the mineral content of hay. It is generally recommended to soak hay for no longer than 30 minutes in warm water or 60 minutes in cold water. 
Steaming hay helps to reduce airborne particulates and allergens that can cause issues for horses with respiratory problems. However, steaming hay is labour intensive and requires the purchase of an expensive steamer.
8) Train horses to drink flavored water if travel is anticipated
Differences in the taste of water may negatively impact your horse’s intake and hydration status. This is particularly problematic for horses that are travelling.
It is recommended to get your horse used to drinking flavoured water prior to transport. This will help to offset any differences in the taste of the water they are used to and the potential novel water source at their destination.
Water can be flavoured with apple juice, Gatorade, commercial flavouring, an electrolyte product, or sugar. The flavour should slowly be added to the water in increasing quantity for 1 â€“ 2 weeks prior to transport. 
If you have a metabolic horse, speak with a nutritionist to learn about appropriate flavouring solutions and safe quantities of sugar.
We’ve all heard the famous saying: “You can lead a horse to water, but you canâ€™t make them drink“.
However, there are certain factors that can both negatively and positively impact water consumption in the horse.
Ensuring that your horse is well-hydrated is of utmost importance for maintaining optimal physical performance and health; especially if they are undergoing moderate or heavy exercise or live in hot and humid conditions.
Giving your horse free access to clean fresh water and providing additional salt and electrolytes are the simplest ways to encourage adequate water intake.
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