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Blue-green algae poses threat

by Wyoming Livestock Roundup

The Water Quality Division of the Wyoming Department of Environmental Quality (DEQ), along with the Wyoming Department of Health (WDH) and the Wyoming Livestock Board released a statement in June as summer temperatures began to heat up reminding people to avoid cyanobacterial blooms and report any suspected illness to the DEQ and WDH.  

In a recent University of Nebraska-Lincoln (UNL) Beefwatch podcast and newsletter, UNL Extension Educator Amy Timmerman shared the dangers of cyanotoxins produced by blue-green algae to livestock and wildlife.  

“We typically see blue-green algae in situations where drought conditions have existed,” she explains. “Luckily, we have seen very timely rains in the region, but in drought-like conditions, blue-green algae can occur in ponds and dugouts, or in any water source where water is stagnant.”  

The DEQ explains, harmful cyanobacterial blooms (HCBs) have the ability to produce toxins and other irritants which pose a risk to both human an animal health.  

Livestock concerns 

“We’ve heard about the risk of blue-green algae to humans, especially through recreational lake closures, but this is also harmful to livestock and wildlife,” Timmerman shares. “While not all blue-green algae produces a toxin, this toxin is very dangerous for livestock to consume.”  

Often, livestock stand in pasture water sources, especially when it is hot, Timmerman notes. This action increases the amount of manure, and in turn, nitrogen in the water. Blue-green algae feeds off of nitrogen and phosphorus within a water source.  

“Once concentrations are high enough, symptoms of toxicity poisoning appear in full-size cattle anywhere from two to 24 hours after consumption,” she continues. “It doesn’t take very long at all before we see impacts to cattle health.” 

Signs of cyanotoxin poisoning include neurological symptoms, such as weakness, staggering, difficulty breathing, paddling and convulsions, Timmerman shares. Additionally, the toxin affects the liver and producers may see a pale color in mucus membranes, overall weakness and bloody diarrhea. Severe infection of the toxin may lead to death of the animal.  

Spotting HCBs 

To look for potential harmful blooms of blue-green algae, Timmerman recommends producers view the leeward or downwind side of the water source. Any blue-green, red, yellow or green scum on top of the water could be indicative of blue-green algae growing on the water surface.  

Additionally, Timmerman shares producers should look around to see if any wildlife, including dead fish, snakes, frogs or rabbits, are in the area. If any blooms are spotted, producers should take action to keep livestock from utilizing these water sources.  

“If cattle do consume toxic blue-green algae, there is no antidote,” Timmerman says. “Animals that only consume a small dose do recover, but recovery is slow and producers will see a loss in weight. Lighter colored cattle, such as Charolais and any white-faced cattle tend to become photosensitive and will need a few weeks to recover from skin damage.”  

While not all blue-green algae blooms are toxic, it is important to watch closely and test if needed.  


If producers notice HCBs being a consistent problem, they can take action to keep their livestock safe. First, Timmerman recommends fencing a problem water area off from livestock. Second, producers can bring in an alternative water source, and for those who have the ability, can pump contaminated water out of the tank.  

“Blue-green algae is only typically found on the top six inches of a water source, so if it is possible to remove water, cattle will be able to utilize the water source again without hauling water,” Timmerman says.  

She continues, “Depending on where ponds or dugouts are, implementing a good nutrient management program and grazing management plan can help prevent blue-green algae toxicity. The one big thing is we want to graze pastures correctly and make sure there is plenty of vegetation to catch water before it washes into a dugout.”  

Research has indicated maintaining buffer strips of perennial plants surrounding a pond both encourages cattle not to overgraze, but also acts as a nutrient buffer. 

“Another preventative action is to keep livestock from loitering in water, which is especially difficult in hot weather, or forcing cattle to drink on the windward side of the water source,” notes Timmerman. “Last, if producers are constructing a new pond of dugout, I recommend the water source to be at least 20 feet wide, 80 feet long and 10 feet deep to avoid wind impacts and ensure the water is deep enough to pump out if it is needed.”  

Averi Hales is the editor of the Wyoming Livestock Roundup. Send comments on this article to 

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