Watch for Cyanobacterial Poisoning in Livestock

August 7, 2015 10:48 AM

Cyanobacteria, also known as blue-green algae, is toxic to livestock.

Livestock producers need to watch for blue-green algae because it is toxic to animals, North Dakota State University Extension Service livestock experts warn.

“The hot, dry, calm days common in late summer are the perfect catalyst for the production of cyanobacteria, widely known as blue-green algae,” Extension livestock environmental stewardship specialist Miranda Meehan says.

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. Live cyanobacteria is green. It turns blue after it dies and dries on the surface or shoreline.

Some species of cyanobacteria can be toxic when livestock and wildlife ingest it. The level of toxicity is dependent on the species consuming the water, concentration of bacteria and amount of water ingested. Cyanobacteria produce neuro and liver toxins.

“Signs of neurotoxin poisoning usually appear within 20 minutes of ingestion,” says Gerald Stokka, Extension veterinarian and livestock stewardship specialist. “In animals, symptoms include weakness, staggering, difficulty in 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 in livestock, producers should check the edges of ponds for deceased wildlife. In addition, producers should collect a water sample of at least 500 milliliters from the suspected water source after the discovery of dead livestock or wildlife.

“Water testing only will determine if the water source contains cyanobacteria, not the cause of death,” Meehan says.

Water samples should be submitted to the NDSU Veterinary Diagnostic Lab or a commercial laboratory. For more information on how to submit samples, contact the NDSU lab at (701) 231-8307 or visit its website at

Stokka recommends producers use the following practices to prevent cyanobacterial poisoning in livestock:

  • Implement a nutrient management plan or establish buffer strips with perennial plant species around water sources to reduce the levels of nutrients entering the water.
  • Create a designated drinking area where the risk of cyanobacteria is minimal.
  • Fence off pond and pump water from the pond to the water tank.
  • Use other water sources following periods of hot, dry weather.
  • Add copper sulfate to water if the water source has a history of algae blooms. Apply 2 pounds of copper sulfate per acre-foot of water. That is equal to 8 pounds per 1 million gallons.

Source: NDSU Extension

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