Do You Know What’s In Your Horse’s Water?

two horses drinking water

Did you think that only humans should be concerned with the quality of their drinking water? If you answered yes to that question, you may want to reconsider. Not only is good quality water important to humans, it is both the number one nutrient fed to any animal, as well as the most often overlooked nutrient in the nutritional program of ANY species, including horses.

While there are many studies, guidelines, environmental regulations, requirements, and laws surrounding human drinking water, horses and other livestock usually have access to water that contains excessive levels of contaminates such as minerals, bacteria, algae, fertilizer, protozoa, and viruses. All contaminates can be dangerous, but some contaminates, depending on their composition and levels, can be deadly to your horses and other livestock.

horse foraging Horses, by weight, consume two to three times the amount of water as they do food. It’s not hard, therefore, to understand how the ingestion of contaminated water might negatively affect the health of your horse. Generally, horses should consume enough clean water daily to replace what they lose through sweat, urine, and feces. To retain essential electrolyte and nutritional balance necessary in all horses, but especially in the performance horse, particular attention should be paid to the amount of water lost through sweat during exercise.

Not so different from humans, sweating is an important factor in how your horse maintains its core temperature. In high temperatures, horses tend to eat less and drink more, but if the environmental humidity is high (over 80 percent), sweating will not effectively cool the horse, putting him at risk for overheating. Horses can lose up to three gallons of sweat per hour during normal exercise, but that amount can increase significantly depending on the level of exercise and other environmental factors such as temperature and humidity.

But there are other factors that contribute to proper water consumption levels for your horse other than their ambient environment (temperature and humidity) such as the quality, type and amount of feed, overall health of the horse, and physical activity levels. For example, under normal activity and weather conditions, the daily base level for proper hydration of a horse weighing 1,100 pounds would be approximately one gallon of water per 100 pounds of body weight, or 11 gallons of water per day. If, however, that same horse was in training for or participating in a performance event, he could easily need to consume a whopping 33 gallons of water per day to remain sufficiently hydrated !

Most Common Water Sources For Horses

horse drinking from a stream Let’s face it, unlike us, bottled water is NOT a common source of water for our horses. And although water filtration systems are commercially available that can be added to a barn from complex systems connected to a farm’s main water supply to simple charcoal filters attached to a hose, they may not be a practical addition for some barns. And then there are the pastures, paddocks, and natural streams or other groundwater sources that fill the better part of our horse’s day. The fact is, although we think we are providing our horses with clean, fresh water, this just may not be the case!

What Are Water Contaminants?

It would be impossible to list all of the currently known water contaminants, let alone ponder all of the possible considerations that have yet to be identified. Contaminants have, however, been identified in many forms and through a wide variety of sources that appear both randomly through nature and as a consequence of human-introduction, whether intentionally or unintentionally.

For example, minerals (produced through nature) are present in all water, but high concentrations of some minerals can cause chronic or even toxic effects in animals. For example, water containing less than 400 mg/L of nitrite is generally safe, yet levels in excess of 1500 mg/L may be toxic. In horses, however, nitrite is 10 to 15 times more toxic making levels of nitrite that exceed 30 mg/L potentially hazardous to your horse’s health.

horse drinking dirty water Likewise, cyanobacteria (blue-green algae), found most often in groundwater contaminated by fertilizer, contains toxins that can cause liver damage to horses and other livestock. Groundwater is also a common source for a variety of viral, bacterial, and protozoal contaminates that may cause serious health issues for your livestock and horses. And don’t let the clarity of most groundwater fool you. Although most groundwater will normally look clear and clean, it can be hiding both natural and human-induced chemicals. The process is a simple one. As groundwater flows through the ground it picks up naturally-appearing minerals from the soil such as iron and manganese, as well as human-induced contaminants such as pesticides, fertilizers, or remnants from leaking fuel tanks or toxic chemical spills to name a few. And bacteria may have also been introduced into the groundwater from such sources as leaking septic tanks or waste disposal sites.

Did you know that the taste of water is often determined by its mineral content, most notably chlorine, potassium and sodium, or that taste influences water consumption? So when minerals in your horse’s water supply get out of balance, the horse may instinctively respond by decreasing its water intake, which may in turn negatively affect many of its physiological functions.

Other examples of potential water contaminants include herbicides, pesticides, nutrients such as Chloride, which is chemically the same as the possibly toxic chemical chlorine, and even drugs, just to name a few. And the reactions may not be a direct correlation, but rather they may be complex and diverted. For example, water that is too high in nitrates can affect vitamin A and selenium absorption, which in turn can affect your horse’s effective use of vitamins D, E, or B complex. Nitrites can also cause displacement of oxygen on the hemoglobin molecule. This reaction reduces the transport of vital oxygen to the horse’s tissues, which eventually results in respiratory distress. And where do nitrites come from? In groundwater, the most common source of nitrite contamination is runoff of fertilizer and manure from agricultural land.

Even the amount of dissolved salts in water can be a contaminant in excessive quantities. Water with a salinity level up to 4,000 mg/L should be no problem for your horses. Drinking water with levels between 4,000 – 6,000 mg/L may produce some hesitation to drink by the horse, and even some diarrhea, but they should eventually adjust without any serious health issues. However, drinking water with salinity levels above 6,000 mg/L will most likely cause problems.

Management Tips For Healthy Horses and Clean Water

Water Test

horse water testing Drinking water for your horses and other livestock should be tested periodically for toxins, chloride, bacteria, and high levels of minerals.

A typical water analyses should include the following tests:

  • Total coliform bacteria
  • pH (acid or alkaline level)
  • Total dissolved solids
  • Total soluble salt
  • Salinity
  • Hardness
  • Nitrates
  • Sulfate
  • Other factors such as toxicity problems with specific minerals or pesticides, or occasionally, heavy algae growth

Commercial Filtration Systems

As mentioned earlier, there are numerous water filtration systems that are commercially available, but we all know that this solution may not be neither viable nor practical to many a horse owner. So what are some more practical steps you can take to help protect the integrity of your horse’s water quality?

Supplements and Treatments

Minerals can be fed individually or mineral supplements can be balanced to counteract imbalances in excessively mineralized drinking water. Homeopathic treatments, as well as herbal and nutritional supplements are available to aid in the detoxification process.

Pastures and Paddocks

Just remember that what’s good for the horse is good for the water. Maintaining an un-grazed vegetated border around streams will help protect the water from excessive heating, reduces trampling to help stabilize banks, and protects against manure polluting the water. The added vegetation will also serve as a filter strip for possible contaminants lurking in run-off.

Ways To Keep Your Water Clean

Erect fences to keep horses out of canals and ditches to protect the cleanliness of irrigation water that might drain into a nearby stream. Consider a hose pump or water trough to provide a safer source of drinking water for your horses.

Allow Grazing Between 8″ and 4″

horses eating grass Graze at 8, no more at 4….graze your horses in pastures when the grass is about 8” tall and remove them at 4” to allow the grass to re-grow. Over-grazed pastures contribute significantly to surface water run-off, soil erosion, and less forage. Instead of one large pasture, consider cross-fencing your pasture into smaller pastures so that you can rotate your horses, allowing each pasture some rest that allows not only the re-growth of grass, but also to allow any parasite larvae to die in the sun.

Harrow Your Pasture

Fifty pounds of manure! Yikes! That’s what an average 1000-pound horse produces PER DAY! That’s roughly 9 tons, or 6 pick-up loads per year. Harrow your pastures regularly to incorporate manure into the soil. This is important pasture management to help expose parasite larvae to sunlight and preventing bacteria and nutrients from seeping into groundwater. Without proper harrowing, horses tend to designate one area of the pasture as their “bathroom” and understandably under-graze it, while over-grazing others. Harrowing tends to promote more uniform grazing.

Provide Sufficient Drainage

To reduce mud and dust in your pastures, use sand, wood chips, or other acceptable fillers to provide sufficient drainage. Consider using gutters and downspouts on buildings to divert snowmelt and rainwater around your paddock while any run-off should be diverted toward vegetative filter strips if possible. A well-maintained paddock will have little to no contaminated run-off or groundwater.

Professional Assistance

horse stable Remember that water quality can be affected by conditions or events that occur far away from your farm, so be alert to your animals’ behavior. If you suspect that the water source for your horses or other livestock is causing health problems for the animals, seek veterinary assistance. Diagnostic testing may be necessary of the animals, as well as the water supply to properly evaluate the problem.


The BOTTOM LINE is that although the U.S. Environmental Protective Agency (EPA) provides recommendation regarding safe standards for livestock drinking water, there are no current regulations governing those recommendations. As of now, the quality of your horse’s drinking water is entirely in your hands.

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