Cyanobacteria, also known as blue-green algae, can produce toxins that are harmful to livestock, wildlife and people.

Blue-green algae often occurs in stagnant ponds or dugouts with elevated nutrient levels, forming large colonies that appear as scum on or just below the water surface. The scum can resemble green paint. Water can also appear blue to brownish green.

Cyanobacteria typically become a concern beginning in mid-July through late summer and early fall especially in calm, shallow water bodies. Occasionally, mild spring weather and warm water can also create ideal conditions for algal blooms to occur.

Some species of cyanobacteria can be toxic when livestock and wildlife ingest them. Toxicity is dependent on the species consuming the water, the concentration of the toxin or toxins and the amount of water ingested.

Cyanobacteria can produce neuro and liver toxins. Signs of neurotoxin poisoning can appear within five minutes to up to several hours after ingestion. In animals, symptoms include weakness, staggering, muscle tremors, difficulty breathing, convulsions and, ultimately, death.

Animals affected by liver toxins may exhibit weakness, pale-colored mucous membranes, mental derangement, bloody diarrhea and, ultimately, death.

Typically, livestock are found dead before producers observe symptoms. If cyanobacterial poisoning is suspected as the cause of death, producers should check the edges of ponds for dead wildlife. Dead wildlife is an indication that cyanobacteria are in the water.

In addition, producers should collect a water sample from the suspected water source and submit it to the NDSU Veterinary Diagnostic Laboratory or a commercial laboratory.

When collecting a water sample, follow NDSU Extension’s “Livestock Water Testing Guidelines” (“https://tinyurl.com/NDSU-LivestockWaterTesting”>tinyurl.com/NDSU-LivestockWaterTesting).

Be sure to wear gloves because cyanobacteria can be toxic to humans. Collect a sample of the suspected cyanobacterial bloom from the surface of the water and deeper in the water. The sample should be kept cool but not frozen, and submit it to the NDSU Veterinary Diagnostic Laboratory or a commercial laboratory.

Here are some ways producers can prevent cyanobacterial poisoning of livestock:

– Reduce nutrient levels entering the water source by implementing a nutrient management plan or establishing buffer strips with perennial plant species.

– Create a designated drinking area where the risk of cyanobacteria is minimal.

– Fence off the pond and pump water from the pond to the water tank.

– Use water from other sources following periods of hot, dry weather.

– Add copper sulfate to the water if the water has a history of algae blooms. Apply 2 pounds of copper sulfate per acre-foot of water, which is equal to a rate of 8 pounds per 1 million gallons. Livestock must be fenced out of treated water sources for at least 10 days.

For more information, check out NDSU Extension’s “Cyanobacteria (Blue-green Algae) Poisoning” publication at tinyurl.com/NDSU-blue-green-algae.

Schmidt is the NDSU Extension agent for Pierce County.