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September 15, 2011

How much water does my horse need? – post 2 of 3 part series

by DePaolo Equine Concepts

Water requirements for healthy electrolyte balance and proper hydration vary greatly based upon a horse’s activity level, feed program, age, weight and mental state[1].  As a rule of thumb, active horses will require a water intake increase of up to 300% during heavy and prolonged exercise.

  • Horse at Rest : in a temperate climate this is approximately 5 to 10 gallons per day.  The number goes up some if the weather is warmer or if the horse lives in a hot and enclosed barn.
  • Horse at Rest on Pasture: lush pasture can contain 60-80% moisture and provide a horse with a larger portion of its daily 5 to 10 gallons of water when at rest. Horses that are kept on dry lots may actually increase their intake due to hot conditions and dry forage.
  • Horses Fed Alfalfa and High Protein Diets: horses that eat primarily alfalfa or large quantities of concentrates will require different amounts of water in order to meet the demands of digestion of the protein than horses fed in pasture. Often, stabled horses are fed too much protein which the body attempts to flush out via increased water intake. Horses that are fed a forage-only diet of grass hay are likely to drink 26% more than horses that are fed concentrates or alfalfa.  This is one reason why many veterinarians and nutritionists recommend cutting back on proteins and concentrates and encourage hay-only diets.
  • Overweight Horses: because body fat is low in water content, fat overweight horses require less water intake than do horses in leaner body condition.
  • Horses Who Live In Cold Climates: horses are likely to decrease their water intake by as much as 14% when the weather is consistently cold.   While it is common to supply slightly warm water to horses in cold climates, new studies show that horses drink the most when they are offered water that is around 68 degrees.  Horses that are kept at pasture will often choose cold water from natural sources over the heated water offered by their owners.  The reasons for this are still unclear but definitely suggest that it is best to keep water around room temperature for optimal consumption.
  •  Horses in Hot Climates: Horses that live in hot conditions can have water intakes that are as much as 79% above that of horses in moderate climates.  Horses will sweat even standing in their stalls if the ambient temperature is high enough and subsequently lose valuable electrolytes if they are not offered enough water.  The challenge in hot climates for providing water at the appropriate temperature is that cooling the water source is much less practical than warming it.  One way to combat this problem is to provide access to a salt block or to top dress the horse’s feed with salt to encourage a thirst response.
  • Lactating mares: Lactating mares and equine athletes require the most water intake.  It is thought that mares lose as much water as equine athletes due to milk secretion and subsequent increased forage intake to create milk. Lactating mares may drink up to twenty gallons a day.
  • Equine Athletes: The equine performance horse produces a significant amount of metabolic heat when exercising.  This metabolic heat can cause horses under heavy work to lose around 3.2 gallons of moisture just through sweating alone.[2] A horse being worked hard can require around 23 gallons of water a day to maintain proper hydration.
  • Horses with Cushings or Renal Problems: Horses that have Cushings, pituitary conditions or renal issues will require more water than healthy horses in varying amounts depending upon the severity of their disease.  These horses are best monitored by a veterinarian and put on appropriate treatment plans to attempt to control the disease that is causing them to consume too much water.  Horses that are over-consuming water can cause imbalances nearly as severe as those caused by a lack of consumption.
  • Foals: Foals obtain their necessary water via the mare’s milk for the first 18 days of their life. After that, they actually require nearly as much water proportionately as an adult horse in addition to their water intake from their mother’s milk.  Foals up to 44 days old will need about 1 gallon of water a day and foals 60-74 days of age will need 1.5 gallons to around 2 gallons.
  • Horses with Diarrhea: Horses who are sick or have a digestive upset of any kind will require more water than a healthy horse at rest in order to combat the moisture that is being lost via loose stools.  Typically the horse absorbs much of the moisture in its diet via its large and small colons. When food travels through them too quickly, the body does not properly absorb the fluid portion of the colon contents and it passes with the manure.  Horses that maintain water intake during an illness or a digestive upset are probably not at risk for further complications, but horses who are very ill often suffer depression and decrease their fluid intake.  Horses with digestive upsets who do not drink enough water often suffer from severe electrolyte imbalance due to the necessary sodium, chloride and potassium that is being removed from the body along with the diarrhea.  Often these necessary electrolytes need replacement to make the horse feel better and to correct the digestive upset.

Next week we will be discussing how to test for proper hydration in your horse and if you missed our first post about water in the body, please read!


[1] Feedstuffs “Water Most Overlooked Nutrient For Horses” Joe D. Pagan

[2] The horse.com “Dehydration Alert”. Les Sellnow. July 1, 2001

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