Home Horse Care Blue-Green Algae And Horses: Here’s What You Need to Know

Blue-Green Algae And Horses: Here’s What You Need to Know

by Amber King

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In North Carolina, three dogs died after swimming in a pond. In Texas, three more dogs died after spending time with their families at a popular lake. You’ll find similar stories of heartbreak in states including Oregon, Minnesota, and Florida. All of these dogs died due to a toxic substance called blue-green algae, but there’s something the news stories are leaving out. Blue-green algae is a highly toxic substance that grows in nutrient-rich bodies of water in warm weather. Dogs may be the most at risk, but other animals, including your horses, are also in danger of being poisoned. 

What Exactly Is Blue-Green Algae?

Also known as cyanobacteria, blue-green algae are a type of bacteria that thrive in nutrient-rich bodies of water. When the weather is warm and the right nutrients are present, the algae blooms and spreads across water. It depletes the oxygen level of the water (often killing fish and plants), and leaves anyone who comes in contact with the water at risk of poisoning.

Image by Deedster from Pixabay

Where Are Blue-Green Algae Found?

As far as location, blue-green algae can be found in most areas of the United States. There have been several cases in southeastern states including North Carolina and Georgia, but location doesn’t seem to matter as much as the conditions of the water. 

This type of toxic algae prefers calm water and temperatures higher than 75 degrees Fahrenheit. The stagnant waters of lakes and ponds are ideal environments, but it has also been found in slow-moving streams and brackish water ecosystems.

Image by Marc Pascual from Pixabay

Horse farms with ponds and other natural water sources are especially at risk. Many horse farms are located near fields where farmers use manure and other types of fertilizers to nourish their crops. When it rains, runoff from those fields is sent across the land, and some of it ends up in ponds and lakes. The nutrients found in fertilizer are exactly what blue-green algae need to thrive. 

Use this interactive map to locate active algae blooms near you.

How Blue-Green Algae Affects Horses

The toxins in blue-green algae are harmful to all animals–and that includes horses. Your horse’s biggest advantage when it comes to fighting of the effects is size, but drinking from an algae-infested pond or lake is still dangerous. A toxin called microcystin attacks the gastrointestinal tract and can cause severe colic and diarrhea in horses. If a horse drinks enough of the water or swims in the pond, they could be susceptible to severe liver damage that could end up being fatal. 

Image by Gary Chambers from Pixabay

How to Protect Your Horses

If your horses have access to a natural water source on your property, it’s important to inspect it for signs of toxic algae. Sometimes the algae blooms look like someone spilled bright green paint into the water, but that isn’t always the case. Blooms can also be disguised as floating debris that has a greenish tint. If you’re unsure, it’s best to stay on the safe side and assume the worst. Block off access to the water and provide your horses with an alternative clean water source.

Unfortunately, there is no way to remove blue-green algae from the water. It’s part of the natural ecosystem, and it’s here to stay. What you can do, however, is limit the amount of nutrients that enter the water. Reduce the amount of nitrogen and phosphorus fertilizer used on nearby fields and lawns. It won’t be an immediate solution, but it will minimize algae blooms in the long term.

If you suspect your horse has been exposed to toxic algae, contact a veterinarian immediately. 

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