Water: The Important Nutrient Everyone Forgets

Posted by Joyce Harman, DVM on Jul 21st 2022

Water: The Important Nutrient Everyone Forgets

Water The Important Nutrient Everyone Forgets

Water is the number one nutrient fed to any animal and is often the most overlooked nutrient in any species’ nutritional program. By weight, horses consume two to three times as much water as food. If the water contains toxins, high levels of minerals or any other unbalanced agent or nutritional problems can result. The media frequently reports that water quality throughout the world is suspect; even well water and spring water found in the countryside far from the polluted cities. Bottled water quality is often suspect also. There have been reports of contamination and of municipal water being bottled as spring water.


Horses should consume enough water to replace what is lost through feces, urine and sweat. Consumption depends on several variable factors:

  • Environmental temperature and humidity
  • Feed quality, type and amount of feed
  • Physical activity level
  • General health

An average amount would be approximately one gallon (3.78 liters) of water per 100 pounds (45 kg) body weight per day. So, a 1,100-pound (500 kg) horse‘s base level might be drinking about 11 gallons (42 liters) of water per day in normal, average weather conditions. The same horse training hard for a Three-Day Event could consume about 33 gallons (125 liters) of water per day. Mares in lactation can increase their water consumption by about 50 to 80 percent for milk production.

In all horses, but most importantly in the performance horse, the amount of water required per day is dependent on the amount lost through sweat during exercise. Sweating is an important function in maintaining the core temperature of the horse. Horses can lose up to 3 gallons (12 liters) of sweat per hour. Therefore, that same Thoroughbred competing in the Three-Day Event would require more water after completing the cross-country course than it would after the dressage test because it worked harder for a longer period of time, causing it to sweat more. Temperature and humidity will also affect water loss from the horse. Horses generally drink more and eat less when the temperature is high. In an environment with high relative humidity (over 80 percent), sweating does not efficiently cool the horse, despite increased water intake.


Herbicides and pesticides are designed to throw the plant or insect out of balance. A quart or so will often treat many acres of land after it has been diluted. The waterways and aquifers have become large vats for these diluted combinations of herbicides and pesticides mixed together. Yet, nothing is known about the effects of these chemicals in combination. Herbicides and pesticides are often considered endocrine disruptors, which means they adversely affect the hormonal system. (https://www.ewg.org/venturamapmethods). This contributes to our increasing incidence of Insulin Resistance and PPID (or Cushing’s as it’s incorrectly called).

Chloride is an important nutrient that has been identified as being in excess of much of the water supply, and most certainly in urban chlorinated sources. Chloride is chemically the same as chlorine, the chemical used to sterilize or clean water when there is excessive bacterial growth. Evidence is mounting that chlorinated water is toxic and may contribute to or be a cause of cancer in people. No specific data has been generated in horses yet; however, there is every reason to expect similar potential illnesses or negative health effects.

Drugs are also present in water supplies, and not just in urban areas. No research has been done on the accumulative effects of the low levels of many types of drugs found in the water supplies. But there are well-documented changes in aquatic life, with sterile individuals, deformed fish and amphibians and others. (Note: see references below for links to articles. There are many more contaminants present in water).


Water consumption is influenced by taste, which is often determined by mineral content, in particular by chlorine, potassium, sulfur and sodium. The animal tries to maintain an internal balance, and minerals affect physiologic function, so water intake is decreased if the minerals are getting out of balance.

Water can have an excess of a particular mineral or ingredient such as nitrates, iron or copper. Nitrates can affect vitamin A and selenium absorption. Without vitamin A, the body cannot use vitamin D, E or the full B complex vitamins.

High iron in the water has an indirect effect on calcium and phosphorous. This occurs because phosphorous is the closest to iron in atomic weight; high iron impedes the utilization of phosphorous, which in turn affects the availability of calcium. However, it is not a calcium deficiency; it is a phosphorus and iron problem. Sometimes the mineral content of water is seen as a precipitate (i.e., white, green or other colored deposit). Sometimes the water looks totally normal yet contains high levels of certain minerals.


Water nutrients must be taken into consideration if you are trying to calculate mineral intake. Horses take nutrients from feed, forage (grass and hays), and water. It’s fine to calculate in detail what you are feeding in the grain bucket, but there is little point in being precise if the amount consumed in water throws the balance off. In many cases, it’s best to use a free-choice mineral system and let the horse help with the balancing. (https://shop.harmanyequine.com/shop/joints-muscles/joint-health-equine/rush-creek-minerals-free-choice-organic-minerals/) or (https://shop.harmanyequine.com/shop/basic-nutritiontreats/free-choice-stress-systemby-advanced-biological-concepts/).

Water quality or contamination affects the soil directly, since water carries nutrients and toxins across the surface and into the groundwater supply. The soil that the grass and hay is grown in may contain the residue from heavy duty farming practices or run off from neighboring farms before it became used for grazing. Many locations were subject to biosolid or sludge applications for years. Biosolid is a “nice” word for municipal waste applied as a fertilizer to farmers’ fields, often for free. Heavy metals accumulate in the soil, but when the land is developed, those heavy metals remain. Our horses graze the grass growing there, or a future farmer harvests hay without knowing what was on the land years before. Rainfall or flooding can bring contaminants from far away.


The best way to manage the potability of the water source is to test for toxins, high levels of minerals, chloride and bacteria through standard water analysis. Many other tests are available; however, it is best to know what you want to test for, since many tests are expensive.

Since it may not be possible to correct water quality issues, you can feed and supplement with high-quality products to help detoxify and support the horse. Clays such as bentonite absorb toxins in the gut. Mineral supplements can be balanced to counteract imbalances in heavily mineralized water. Nutritional supplements, as well as herbal and homeopathic treatments, can aid in the detoxification process.

Hair analysis can be done to help sort out what toxins or nutrient imbalances that might be present. The lab we use is Depaolo Equine Concepts (https://www.depaoloequineconcepts.com/). Detoxification and custom balancing formulas can be prepared based on the analysis and are helpful.


Many horses live in urban areas, with urban water supplies that may have fluoride added (another toxin). Some stables give horses water they will not allow people to drink. Many people drink bottled water; however, it is not practical to do that for horses. Water filters can be added to a barn, but if it is a boarding barn that may not be practical. Many systems to filter water are expensive when looking at the volume of water used by a large commercial barn. Filters of many sorts can be used, from simple charcoal filters attached to the hose, to complex systems attached to the main water intake for the farm.

A good resource for compact and portable water filters that can be adapted to barn use is an RV supply store. There are many on the internet or locally. https://waterfiltersofamerica.com/rv-filters-and-softeners/. It’s important to find out what you need to filter, since the type of contaminant or nutrient determines the type of filter.