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Blue-Green Algae a Threat to Livestock

University of Minnesota Extension, Stearns County News
August 30, 2017        
Source:  Emily Wilmes, Extension Educator-Livestock
University of Minnesota Extension
Stearns, Benton & Morrison Counties

Blue-Green Algae a Threat to Livestock
By Emily Wilmes, University of Minnesota Extension

ST. CLOUD, Minn. (08/30/2017) — The time of year and recent high temperatures make many Minnesota waters at risk for blue-green algae blooms.  This is a concern for Minnesota livestock farms, as blue-green algae is toxic to both animals and humans.  First thing’s first, what is blue-green algae?  It is actually not algae, but a kind of bacteria called cyanobacteria.  Blue-green algae prefer sunny weather and water temperatures higher than 75 °F, as well as low wind speeds.  Blooms usually occur during summer and early fall.  Harmful blue-green algae can be found everywhere in Minnesota, but thrive in warm, shallow, lakes and ponds.  Blue-green algal blooms are often described as looking like pea soup or spilled green paint.

If you have livestock near ponds, lakes, or other bodies of water, inspect the area for signs of blue-green algae blooms.  Blue-green algae has also been known to grow in stock tanks and water troughs.  If you’re concerned there is a blue-green algae bloom present, remove your animals from the pasture or pen with that water source.  Testing for blue-green algae is possible, and requires a sample of one part water, one part 10% formalin sent to a diagnostic lab. 

Blue-green algae blooms can contain neurotoxins, which cause nervous system damage, or hepatotoxins, which cause liver damage. If water contaminated with blue-green algae is consumed by livestock, death will typically occur within 24 hours or less after ingestion. Livestock and humans are all susceptible to this toxins, as well as pets. The most common sign of toxicity from blue-green algae is finding a dead animal close to the contaminated water. Because death occurs so quickly, there is not a typical treatment for blue-green algae exposure. 

Prevention of exposure is key.  Livestock should be removed from contaminated water and supplied with fresh water from another source.  Because the blooms float near the edges, water can be pumped from the bottom and middle of an affected stock pond if need be.  Blue-green algae thrives in nutrient-rich water; blooms can be prevented by reducing nutrients in a pond or water body via a nutrient management plan and buffer strips.

Blue-green algae is a threat to both livestock and humans.  If you’re concerned about a possible blue-green algae bloom in your livestock water source, move the animals off of the area immediately and consider getting the water tested at a diagnostic lab.


Emily Wilmes
Extension Educator, Ag Production Systems - Livestock
(320) 255-6169
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