Our Privacy/Cookie Policy contains detailed information about the types of cookies & related technology on our site, and some ways to opt out. By using the site, you agree to the uses of cookies and other technology as outlined in our Policy, and to our Terms of Use.


Can a Horse Get Sick From Drinking Stagnant Water?

i George Doyle/Stockbyte/Getty Images

Don’t assume that just because your horse is drinking from a water source that the water must be OK. Some horses are simply more willing to drink, especially after exercise or in hot weather. It’s up to you to ensure that your horse's water is clean and fresh, and that any water containers are clean, as well. A good rule of thumb is that if you wrinkle up your nose when you look at your horse’s water supply, you should question its suitability for your horse.

Stagnant Water is Always Contaminated

According to equine veterinarian Janet Roark of Austin, Texas, it’s safe to say that all stagnant water is contaminated -- just what it’s contaminated with will determine what illness your horse may end up contracting from drinking it. “Mosquitoes breed in stagnant water, and are the source of transmission for such viruses as West Nile virus, Western equine encephalitis and Eastern equine encephalitis,” says Roark. “Rodents such as mice and rats gravitate toward stagnant water and can contaminate it with excrement.” The bottom line, according to Dr. Roark: "If you can remove all stagnant water from your property, your horse will be better off."

Warm Weather Woes

When the weather entices your horse to drink more water, you have to be diligent about preventing stagnation. During warm weather algae grows quickly, sometimes in a matter of hours, and can become toxic. In extreme cases your horse can suffer muscle and organ damage from blue-green algae toxins. Just the smell of stagnant water can be enough to turn off some horses from drinking any water, or as much as they should. When the temperature goes up, this can be especially dangerous to your horse; she needs water to move her food through her stomach so drinking less than the optimum amount -- about 12 gallons a day -- can lead to colic or at a minimum, dehydration.

Contaminant Sources

If your horse is turned out or pastured with a natural water source, such as a stock pond or lake, keep in mind that you can’t control its cleanliness, so keep another source available. Contaminants such as urine and manure from horses or other livestock, or fertilizers and pesticides from runoff, can easily infiltrate pond water. Remember that horses can’t vomit, so even if your horse drinks stagnant water willingly it has to go through her system. While Dr. Roark notes that many horses have strong stomachs and may never get sick, there are no guarantees. Illnesses from water contamination can lead to reproductive problems or even aborted foals. Bouts of diarrhea can lead to dehydration and colic.

Cleanliness Measures

Rinse small water containers daily and take a few extra minutes to wipe them down before refilling. Some horse owners put a small amount of bleach in the water supply to inhibit contaminants such as algae, but vinegar -- either white or apple cider -- is a healthier alternative and typically palatable to horses. Change out the water in larger tanks before it looks unappealing to you; a long-handled brush such as a clean toilet brush works well for scrubbing the sides of larger containers. Consider adding fish that will consume algae, such as goldfish, catfish or koi. Check your tanks each day for any animals that may have fallen in and drowned, such as birds or squirrels. Inserting a board or branch that other animals can use to climb out can prevent these mishaps and carcass contamination.