Livestock Update, December 1998
Larry Lawrence, Extension Animal Scientist, Horses, Animal and Poultry
Sciences, Virginia Tech

Nothing has greater influence on the overall well being of the horse than water intake. It affects fluid balance, temperature control, exercise tolerance, and digestibility of feedstuffs. There are two primary concerns for horse owners in relation to water quality. First, is the quality of the water poor enough to affect consumption or cause toxicities and therefore compromise the health of the horse? Second, does the water serve as a carrier for the spread of disease? There are a umber of factors to consider in maximizing water intake.

Maximizing water intake should be a primary goal in the management of horses. Recent surveys have indicated that restricting a horse from water for as little as 2 hours will increase the chances of colic. Temperature is probably the number one factor. When the water temperature increases from just above freezing to 40 degrees Fahrenheit, the amount of water consumed will increase almost 40%.

The quality of the water offered to horses is also a factor determining intake. Testing water may reveal problems that may reduce intake or cause other serious health concerns. But, before you run out and test your water, there are a few facts you should know.

The foremost issue is the source of water. In the summer stagnant ponds, water tanks, and buckets contaminated with algae can lower intake. More importantly, blue-green algae can be toxic to horses. Regular scrubbing with bleach can help eliminate the algae problem. Horses drinking from marshy areas or areas where wildlife or cattle carrying Leptospirosis have access tend to have an increased incidence of moon blindness associated with Leptospirosis infections. Fresh water snails have been identified as a carrier of the agent causing Potomac Horse Fever.

There is some anecdotal evidence that cattle farms with abundant waterfowl have a slightly higher incidence of salmonella disease in their cattle. Whether or not this is true for horses is undetermined at this time. We have always been told that running streams are safe sources of water, however, they have their own special problems. The sands lining coastal beaches originate from mountain streams. Horses drinking from some streams have swallowed enough sand over time to cause colic.

Should we panic and test every source of water for every possible contaminant? Absolutely not. Natural pure water are terms we hear a lot but in fact almost all sources of water contain contaminants. When water comes in contact with air and soil, dissolved minerals, organic compounds and micro-organisms find their way into water supplies. It is only when contamination levels exceed acceptable limits that they become detrimental to human and animal health.

How can we determine if water is safe? If your source of water is from public utilities, it is constantly monitored. If your water comes from a private well or spring, yearly testing is a standard recommendation. Local Co-operative Extension offices and County Health offices are good places to find out about water testing. In general, water tests fall into three categories: biological contaminants, organic chemicals, and inorganic
elements.

Biological contaminants are determined by testing for an indicator bacteria, coliform. Coliform bacteria themselves cause little problem but elevated total coliform counts indicate the water is contaminated with animal or human waste, soil, or decaying vegetation and that the probability exists that other pathogenic (disease-carrying) viruses, bacteria, and protozoa may be present. Total coliform and fecal coliform can be identified in bacteriological analysis. If water does contain coliform bacteria, it is considered an unsanitary supply that may contain waterborne disease-carrying organisms.

When should you test for bacterial contamination? Test when any of the following situations arise:

(1) there is a change in colour, odour, or taste of the water.
(2) when flooding has occurred near the water supply.
(3) any person or animal becomes sick from a suspected waterborne disease.
(4) after maintenance on the water system.

Organic chemicals that may contaminate water include pesticides, polychlorinated biphenyls (PCBs), solvents, and industrial wastes. These find their way into water as the result of spills, improper mixing and application, or illegal dumping. PCBs were outlawed in 1976, however, old dump sites that have not been cleaned and previous misuse may still serve as potential contaminants.

Total Dissolved Solids (TDS) concentration is a standard water quality test that is a measure of organic materials and inorganic metals in water. Increases in TDS are a clear signal for further testing to identify specific problems. The TDS concentration can indicate high levels of one or morecontaminants. Water contaminated with calcium, magnesium, nitrate, nitrite, iron sulphate, copper, lead, and other material may show high TDS levels. Some of these materials cause serious health risk, others are considered nuisance factors.

Water hardness is often a concern for homeowners. High concentrations of calcium and magnesium are associated with hard water. It is interesting to note that many areas of the country known for hard water are limestone based and are also recognized as excellent horse producing areas. The high calcium intakes from water and grazing are reasons given for good bone development. Also, the changes from copper to vinyl pipes in horse operations are partly blamed for lower copper intakes and signs of deficiency in young foals and mares. On the other hand, acid or low pH water and lead pipes are blamed for serious health hazards to young children.

Livestock producers are often concerned with nitrates in water. Nitrates enter the water supply from improper or excessive fertilizer applications or flooding of manure storage areas. Horses are very tolerant of high nitrates. Toxic levels for humans are in the 45 ppm range while there is little concern for horses up to 450 ppm.

The Council for Agricultural Science and Technology reports there are few toxicities to livestock from ingestion of natural constituents in drinking water. In general, horse owners should be conscious of rapid changes in water sources because horses are sensitive to unusual tastes and doors. A yearly test of water sources done after heavy rains or floods or possible contamination by fertilizer, pesticide, or heavy road salt use may be warranted. Other red flag indicators include: signs of waterborne diseases in animals, changes in odour, taste, colour, or when work is done on water systems.