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Horsekeeping Tips: Keep Waterers Clean for Horse HealthBy Kentucky Equine Research Staff · July 13, 2017

In the perfect world, every horse owner would keep his water tanks sparkling clean. In the hustle and bustle world of horse ownership, though, waterers often get short shrift.

Horses drink significant quantities of water. If water is too dirty, unpalatable, or foul-smelling, horses will not drink it, leading to dehydration and other health concerns, including colic.

In general, an idle horse will drink nearly one gallon (3.8 liters) per 100 lb (45 kg) body weight, about 10 gallons (38 liters) for a 1,000-lb (450-kg) horse. Significant variation occurs in how much a horse will drink in a day, and this is due largely to diet. In general, high-fiber diets, such as those composed almost entirely of hay, increase water consumption, while intake of green pasture, which is rich in water, decreases water consumption.

Activity will increase the water requirement, so working horses may easily double their water requirement if they are sweating a lot. Lactating mares have elevated water requirements because milk production requires significant water. Other factors that affect water requirement are an increase in temperature, high humidity, and the intensity and duration of work or competition. Certain diseases, such as Cushing’s, will increase thirst. In a nutshell, supply horses with plenty of clean water at all times, except when they are extremely hot after exertion, during which occasional sips are more appropriate.

When using water tanks that must be filled periodically, opposed to automatic waterers, one of the most prominent problems is algae growth. “A little algae, while unsightly, isn’t a real problem,” according to Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research (KER). “However, it becomes a problem if it makes the water unpalatable and the horse stops drinking.”

During farm visits and consultations, well-read horse owners often ask Crandell about blue-green algae poisoning. “Unchecked algae growth is not beneficial for the ecosystem if it occurs in a pond, as stagnant water and manure are the perfect ingredients for growing blue-green algae. A few species of blue-green algae can produce toxins known to poison livestock,” explained Crandell. “The problem lies in not being able to visually distinguish the algae species in a pond that produce toxins from those that don't. The best method of prevention is to keep the algae growth from getting out of hand.”

Some horse owners will add a drop or two of bleach to a waterer to keep drinking water free of algae.  “Because bleach contains chlorine, it can help sanitize the water. The chlorine in bleach is the same additive used in public water systems. The bleach might help with algae growth for a day but, if the water trough is exposed to sunlight, the chlorine will evaporate in about 24 hours and will no longer be a deterrent for algae growth,” said Crandell. “For horses that are not accustomed, the taste can affect intake although, like city water, they can adapt.”

From time to time, Crandell is also asked about the use of fish in water tanks. “Fish are helpful in the spring, summer, and fall in most areas of the U.S., but it is too cold in the winter for them to survive,” said Crandell, “so they have to be moved to a more temperate environment for a few months of the year.” Fish are particularly helpful if it is a big water trough that is difficult or impossible to clean. The fish, typically goldfish or koi, help control algae growth and mosquito larvae.

A cautionary note: bleach and fish don’t mix, so choose one of these methods to control algae growth but not both.

Some properties have natural water sources available to horses, such as streams and ponds. “If the water is fresh and not too stagnant, streams can be a great source of water for horses. Some streams can be sandy, depending on the geographic region, and these may contribute to sand colic if they are the only water source, especially if coupled with grazing sandy pastures,” said Crandell.

“A pond will work if it isn't too stagnant or has an excessive buildup of algae. A pond might not be appropriate if it is marshy or shared with wildlife or livestock, as there is a chance it can be contaminated with Leptospira, bacteria that can cause disease,” advised Crandell. “There seems to be a direct relationship with the amount of total dissolved solids (TDS) in water and intake.  The higher the TDS, the lower the intake. Murky, muddy ponds are generally higher in TDS.”

Key points:

  • Horses will generally consume one gallon (3.8 liters) of water for every 100 lb (45 kg) of body weight. For most average-size horses, this comes to 10-15 gallons (38-57 liters) of water each day.
  • Keep water tanks as clean as possible. Weekly scrubbing will usually do the trick. Don’t overlook automatic waterers, as they too can become green and slimy with algae growth.
  • A couple drops of bleach or a few fish can help minimize algae growth and are especially useful for tanks that cannot be emptied and scrubbed easily, such as cement structures.
  • Streams and ponds can provide horses with suitable drinking water, but make sure the water looks appealing and isn’t too sandy or muddy.