Water is the most vital component of the equine diet, but it is often overlooked when considering your horse’s nutritional needs.

Hydration influences several aspects of horse health, including exercise tolerance, digestion, and temperature regulation. Not only do you need to ensure that your horse drinks enough water, but also that your horse has good quality water available.

Testing water quality helps to determine whether your horse’s water supply is safe for consumption and whether you need to consider a water treatment or filtration system.

A water analysis will also tell you about the mineral levels present. This can help you address any potential dietary imbalances caused by water intake.

To learn more about water analysis for horses and how horse owners can promote healthy hydration with correct management, continue reading below.

The Importance of Hydration for Horses

Water makes up roughly 70 percent of an adult horse’s body. It is involved in nearly every bodily function, from circulation to digestion and joint lubrication to waste filtration. [1]

A lack of water is an imminent threat to your horse’s vital systems. Dehydrated horses can suffer serious problems such as lethargy, gut impaction, colic and impaired kidney function. [2][16]

Water Intake

An average 1,100lb horse with an idle lifestyle requires 6 to 9 gallons of water daily to support normal bodily functions in thermoneutral conditions. [3]

Higher temperatures and heavier workloads can increase daily intake requirements to 12 to 18 gallons. Lactating mares also need extra water to support milk production. [4]

A horse’s diet also affects water consumption. Horses on pasture get significant amounts of water from eating lush green grass with high moisture content. [5]

If a horse has a high protein diet, it must excrete excess nitrogen via urine. These horses will drink more water to support the increased urine production. [5]

Some environmental conditions can reduce voluntary drinking. For example, some horses drink less water in winter if the water temperature is below 45 degrees Fahrenheit. [6]

Water impurities can also cause reduced intake. Water often contains minerals, bacteria, algae, and other dissolved solids. These substances can impact palatability and voluntary intake.

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Preventing Dehydration in Horses

Horses should have free access to clean, fresh water at all times. [3]

Most horses prefer water between 45 degrees and 65 degrees Fahrenheit. However, evidence suggests that providing lukewarm water with a temperature of 68 degrees Fahrenheit promotes better hydration in cold weather. [6]

Adding plain loose salt to a horse’s diet can also encourage hydration. Salt is a source of sodium, which is an essential mineral that plays a role in stimulating the horse’s thirst response and maintaining fluid balance. [4]

You can also support hydration by feeding your horse an electrolyte supplement in hot weather or after exercise.

Another way to provide water in your horse’s diet is to soak hay or feed. Providing access to grass pasture where available can also increase water intake. [5]

Can Horses Drink Too Much Water?

Yes, horses can drink too much water, but dehydration is much more common. [3] Excessive water intake is most common in horses with PPID/Cushing’s disease or other health conditions that cause abnormal drinking behavior. [7]

Drinking too much water stresses the horse’s kidneys and can interfere with electrolyte balance. [2] However, most healthy horses won’t drink beyond normal limits.

Testing Water Quality

Whether the water source on your horse’s farm is a private well, public water supply, pond, lake, or river, water quality tests are always recommended. [18]

A water analysis looks for physical properties, microbes, mineral levels, and toxic compounds. Testing water regularly during different times of the year and changing periods of rainfall is suggested for accurate results. [8]

Physicochemical properties impacting palatability include water pH, hardness, and salinity. Salinity measures salt concentrations, while hardness refers to the amount of magnesium and calcium in the water.  [12]

Water can also contain other minerals that impact the overall nutrient ratios in a horse’s diet. Water with high levels of bacteria or toxic substances is unsafe for horses to drink. [8]

The following are some of the values usually reported on your water quality analysis.

Total Bacteria Count

The total bacteria count on a water analysis is reported in colony-forming bacterial units (CFU).

Water consumed by horses and other livestock should have a total bacteria count of less than 200 CFU per 100 ml. [9]

Drinking water analyses measure the concentration of two categories of bacteria: total coliforms and fecal coliforms. These bacteria indicate the presence of sewage and animal waste. [9]

Water with a high total bacteria count may have high nitrate levels. Nitrates and bacteria can enter the water supply through surface runoff contaminated with fertilizer. [18]

Total Coliforms

Coliforms represent a large group of bacteria found in the environment, most commonly in the soil.

Total coliform counts may be elevated in water sources affected by surface water runoff. Well water can also be contaminated by microorganisms when structural issues such as broken caps allow debris, insects, or rodents in. [19][20]

Ruminant studies report that coliform counts higher than 1 bacterium per 100 ml cause diarrhea in calves, while older cattle can tolerate water with 20-50 coliforms per 100 ml. [9]

Horse owners could benefit from more research on the effects of acceptable total coliform concentrations in equine subjects.

Fecal Coliforms

The fecal coliform group includes bacteria commonly found in the intestines of warm-blooded animals. [21] E. Coli is a well-known fecal coliform.

This type of bacteria in a water sample can indicate recent fecal contamination, resulting in a greater risk of pathogen exposure. [21]

Horses should not consume any water that contains fecal coliforms unless it is adequately treated. [3]

Nitrates

Nitrate is a naturally occurring form of nitrogen found in fertilizers. Hindgut bacteria can convert nitrates to nitrite, a potentially toxic compound. [22]

Nitrites harm horse and human health because they can limit oxygen transport in blood by displacing oxygen on the hemoglobin molecule. [10]

Horses have more resistance to nitrate toxicity than cattle, but contaminated water can still cause gastrointestinal distress. [9]

Water with nitrate levels of 400 mg/L is generally safe for horses. [23]

Sulfates

Sulfates are sulfur-containing mineral salts that are toxic for horses in high concentrations. [11]

Animal and plant matter decay produces this compound. Some sulfates are also by-products of industrial manufacturing. [11]

While horses have a high tolerance for sulfur, case studies have linked excessive sulfate levels to diarrhea outbreaks and sudden death. [11]

Some areas in North America have water with naturally high levels of sulfur characterized by a rotten egg smell. Unless your water analysis reports concerning sulfate concentrations, slightly elevated sulfur levels generally only impact palatability. [24]

Minerals

Hard water contains high levels of dissolved minerals. In addition to sulfur, other minerals found in some water sources include calcium, magnesium, iron, manganese, fluoride, and sodium. [17]

Hardness is determined primarily by the amount of calcium and magnesium in the water sample. If you suspect your water source is hard, a water analysis can help determine if these concentrations will impact your horse’s health. [12]

Many horse owners have concerns about sources of iron in the equine diet. While most water won’t contain enough iron to risk iron toxicity, high levels of this mineral impact the absorption of other minerals, such as zinc and copper.

Recent research suggests that horses with prolonged exposure to high levels of iron in water, hay, or grass can develop liver disease due to chronic iron overload. [13]

Water pH

The acidity or pH level of your water supply can impact the palatability of water for your horses. [14]

The pH scale measures how acidic or basic a substance is on a range from 0 to 14. Pure water has a natural pH of 7, while a pH of less than 7 indicates acidity.

In one study, horses offered water from a control bucket with a pH of 7.5 drank more than horses offered more acidic water with pH levels of 5.0, 3.6, and 2.9. [14]

Total Dissolved Solids

Total dissolved solids, or TDS, is the total concentration of all substances and contaminants in a water panel test. [17]

The safe upper limit for equine water sources is 6,500 ppm TDS. Fresh water has a TDS below 1,500 ppm, and water is considered saline if the TDS exceeds 5,000 ppm. [15]

Water Management for Horses

Water quality analysis is an important component of managing your horse’s health. Testing water can ensure it is safe for consumption and identify any root cause of palatability problems.

Depending on the results of your water panel test, you may need to implement management strategies to preserve or improve water quality and promote hydration.

Clean Water Sources

Horse owners should keep horse waterers, water buckets, and tanks as clean as possible. Stagnant water and dirty water troughs can threaten your horse’s health by allowing algae, bacteria, and other microbes to grow. [9]

Most horses also find fresh, clean water more palatable. To prevent contamination and reduced intake, water containers should be scrubbed and cleaned at least once a week.

Water Treatment and Filtration

Water treatments or filtration systems can improve water quality by softening, purifying, clarifying, or deodorizing it. [17]

Water filters can remove undesired compounds, organic materials, and other contaminants from the water. [3]

Commercially available water filtration systems can be an incredibly effective solution for water problems.

Water Quality while Travelling with your Horse

If you frequently travel with your horse for competitions or training, you may encounter variable water quality while on the road.

Some horses drink less in new locations due to differences in taste and smell. For short trips, consider bringing your own water with you or purchasing filtered water that you can transport in a portable jug.

You can also counteract palatability issues by treating water with flavoring such as electrolyte powder to encourage horses to drink more. A familiar flavor will ease the transition to a new location.

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Summary

  • Water is the most vital nutrient for equine health and is often overlooked when evaluating equine feeding and management.
  • Poor water quality can reduce palatability and increase the risk of dehydration.
  • Most water contains additional minerals, microbes, and other dissolved solids.
  • Water analysis can ensure that your water is safe for consumption and determine if specific treatments could improve palatability.
  • Strategic water management practices can ensure your horse is getting good quality water and drinking an adequate amount.

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References

  1. Geor, R. et al. Hydration effects on physiological strain of horses during exercise-heat stress. J of Appl Physiol. 1998.
  2. Geor, R. et al. Acute Renal Failure in Horses. Vet Clin North Am Equine Pract. 2007.
  3. Hinton, M. On the Watering of Horses: A Review. Equine Vet J. 1978.
  4. Coenen, M. Exercise and stress: impact on adaptive processes involving water and electrolytes. Livest Product Sci. 2005.
  5. Hyslop, J. Relationship between crude protein intake and water intake in forage-based equine diets. BSAP Occas Pub. 2004.
  6. Kristula, M. et al. Drinking water temperature affects consumption of water during cold weather in ponies. Appl Animal Behav Sci. 1994.
  7. Morgan, R. et al. Dysregulation of Cortisol Metabolism in Equine Pituitary Pars Intermedia Dysfunction. Endocrinology. 2018
  8. Richardson, S. Water analysis: Emerging Contaminants and Current Issues. Analyst Chem. 2009.
  9. LeJeune, J. et al. Livestock Drinking Water Microbiology and the Factors Influencing the Quality of Drinking Water Offered to Cattle. J of Dairy Sci. 2001.
  10. Kim-Shapiro, D. et al. The reaction between nitrite and hemoglobin: the role of nitrite in hemoglobin-mediated hypoxic vasodilation. J or Inorg Biochem. 2005.
  11. Burgess, B. et al. Excessive sulfate and poor water quality as a cause of sudden deaths and an outbreak of diarrhea in horses. Can Vet J. 2010
  12. Elinder, C. et al. Water hardness in relation to cadium accumulation and microscopic signs of cardiovascular disease in horses. Arch Environ Health. 1980.
  13. Theelen, M. Chronic iron overload causing hemochromatosis and hepatopathy in 21 horses and one donkey. Equine Vet J. 2019.
  14. Carson, J. Discrimination of Water Acidity by Mature Horses. J of Equine Vet Sci. 2011.
  15. Corwin, D. et al. Salinity: Electrical conductivity and total dissolved solids. Soil Sci Societ of America J. 2020.
  16. White, N. et al. Treatment of Impaction Colics. Vet Clin North Am Equine Pract. 1997.
  17. Petrovic, M. et al. Analysis and removal of emerging contaminants in wastewater and drinking water. Trends in Analyt Chem. 2003.
  18. Bott, R. et al. Environmental Implication of Nitrogen Output on Horse Operations: A Review. J Equine Vet Sci. 2016.
  19. Reitter, C. et al. Seasonal dynamics in the number and composition of coliform bacteria in drinking water reservoirs. Sci Total Environ. 2021.
  20. Some, S. et al. Microbial pollution of water with special reference to coliform bacteria and their nexus with the environment. Energy Nexus. 2021.
  21. Jamieson, R. et al. Sources and Persistence of Fecal Coliform in a Rural Watershed. Water Qual Res J Canada. 2003.
  22. Tiso, M. et al. Nitrate Reduction to Nitrite, Nitric Oxide, and Ammonia by Gut Bacteria under Physiological Conditions. PLOS ONE. 2015
  23. Oruc, H. et al. Nitrate Poisoning in Horses Associated With Ingestion of Forage and Alfalfa. J Equine Vet Sci. 2010.
  24. Reinhart, K. et al. Capacity of Plants to Accumulate Sulfur and Improve the Quality of Livestock Drinking Water. Rangeland Ecol and Manag. 2021.