Providing horses a continuous supply of clean water is part of the foundation of good husbandry. Several different sources of water might be found on a horse farm: ponds, streams, lakes, and automatic waterers or troughs supplied by well water or city water. (See sidebar.)
It is difficult to find guidelines specific to equine drinking water. Most often, they are lumped into the water quality guidelines for livestock. Following is information to help assure that water quality for your horses is of sufficient quality.
Water samples can be tested for physical and physiochemical properties, excessive nutrients, toxic compounds, and microbes.
Physiochemical properties include salinity, water hardness, and water pH. Salinity is the presence of dissolved substances. Hardness is determined by the water‚Äôs concentration of calcium and magnesium. Excessive water hardness can create mineral deposits on water piping and affect the efficiency of certain disinfectants. Water pH is its level of acidity or alkalinity.
The presence of excessive nutrients, such as sulfates and nitrates, can also be determined by water testing, as can the presence of toxic compounds‚Äîarsenic, fluorine, lead, mercury, and many others.
In a recent issue of the Canadian Veterinary Journal,* a case of water sulfate toxicity was reported in horses. Of a herd of 19 horses, five were found dead, and 13 others had diarrhea. Extensive diagnostic testing of the horses was completed as well as surface water testing and examination of the pastures for toxic weeds. The authors concluded that excessive sulfate levels with high salinity of the surface water caused the illness and deaths.
Fecal coliform measurements can help determine the presence of fecal matter and possible pathogens. Stagnant water can cause excessive growth of bacteria called cyanobacteria, or blue-green algae. In times of drought where surface water levels can become low and water flow decreases or ceases, overgrowth of this bacteria can occur, and cattle have been reported to become sick or die from drinking water contaminated by it.
Floods are the number one costly disaster in the United States. Flood waters can contain sewage, gasoline, oil, petrochemicals, and many other contaminants and are not suitable for livestock as a water source. As soon as is safely possible, animals should be provided a clean source of water in flooded areas.
For advice on water testing, contact your local office of the Cooperative Extension Service (CES) for testing supplies, sample collection instructions, and handling procedures. State CES websites and www.eXtension.org are also good sources of information on water quality and livestock.
*Burgess BA, Lohmann, KL, Blakley BR. (2010). Excessive sulfate and poor water quality as a cause of sudden deaths and an outbreak of diarrhea in horses. Can Vet J 51:277-282.