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An algal bloom in a pond.

How to Protect Livestock from Harmful Algal Blooms (HABs)

Freshwater harmful algal blooms can produce toxins that are harmful to humans, livestock, working animals, and pets. NRCS has several conservation practices that may be useful in protecting animals and people by restricting access to contaminated water or providing alternate water sources.

The ABCs of HABs

An algal bloom in a water body.

Freshwater harmful algal blooms (HABs) are usually caused by rapid growth of blue-green algae (known as cyanobacteria) in water bodies such as lakes, ponds, and streams. These organisms can produce toxins (known as cyanotoxins) that are harmful to humans, livestock, working animals, and pets. Contacting or ingesting contaminated water (including water spray or mist) can result in irritation, illness, or even death.

Cyanobacteria are naturally found in water bodies, so they cannot be eradicated. Instead, it’s important to understand how and why blooms occur. Cyanobacterial blooms and their potential toxicity often are a result of excess nutrients, such as phosphorus and nitrogen, in water bodies. Excess nutrients can come from adjacent agricultural lands, livestock waste, and leaky septic systems, among other sources. HABs typically form in summer, when warm, nutrient-rich, stagnant waters and more frequent sunlight increase the opportunity for their growth.

Treatment of current HABs involves chemical, biological, or mechanical treatment targeted directly at the contaminated waters. Prevention of future HABs involves changing the conditions that favor cyanobacteria, including nutrient management of the surrounding land and trapping or treating nutrient losses to waterbodies..

Risks HABs pose to livestock, working animals, and pets 

Cows in water.

Symptoms* of cyanotoxin exposure in animals include:

  • vomiting
  • excessive salivation
  • fatigue
  • staggered walking
  • difficulty breathing
  • weakness
  • convulsions
  • liver failure

In severe cases, HAB poisoning can lead to death. Therefore, any potential intoxication needs to be immediately addressed by qualified professionals. 

* The USDA Natural Resources Conservation Service (NRCS) is not the authority on HAB symptoms in animals and humans. Please refer to the CDC website for further information, or your state or county health department.

Reduce livestock exposure to HABs

If HABs or cyanotoxins have been detected in a water body, preventing exposure by restricting access is key to ensuring the health and well-being of people, livestock, working animals and pets on the farm. 

NRCS has several conservation practices that may be useful to exclude livestock from contaminated waters or provide alternative water sources. Some examples are:

  • Fencing (382)
  • Pond (378)
  • Access Control (472)
  • Water Well (642)
  • Watering Facility (614)

Steps you can take if a potential exposure to cyanotoxins has occurred:

1. Eliminate access.
2. Wash animals.
3. Provide an alternative water source.
4. Get help with water testing.
5. Monitor the waterbody.
6. Adopt conservation practices to reduce risk of exposure.

Voluntary Conservation Works to Improve Water Quality

Working in partnership with USDA’s Natural Resources Conservation Service (NRCS), farmers are using proven conservation practices to help improve water quality downstream. Our customers are stewards of our nation’s farmland, voluntarily stepping up to the plate to make an impact. They are improving the natural resources in their communities while at the same time boosting the health of their operations for the future.

Water in a stream with woodlands in the background.

For more information

To learn more about how NRCS can help you protect your livestock from harmful algal blooms or for help with other natural resource concerns, contact your local NRCS office.


If you're a farmer or rancher who would like to learn more about how NRCS can help address HAB concerns or other natural resource concerns on your land, contact your local NRCS office.

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