Blue-green algae grabs national headlines each year. News segments highlighting toxic algae blooms leading to lake closures and fish, dog and cattle deaths occur each summer.

Freelance Writer
Denice Rackley is a freelance writer based in Indiana.

With widespread drought and increasing temperatures that exacerbate algae blooms, these stories are not going away, but there are some steps you can take to keep your cattle safe.

Blue-green algae is not an alga; it’s a bacterium – cyanobacteria, to be precise. According to Brittany Chesser, aquatic vegetation management program specialist at Texas A&M’s AgriLife Extension and Aquatic Diagnostic Lab, “Cyanobacteria are present in nearly every body of water and are also found in soils. The name of blue-green algae is misleading because these bacteria can be many colors from bright green, turquoise, red, brown and even clear.

“We see issues with cyanobacteria when periods without rain and elevated water temperatures lead to large amounts of evaporation in smaller bodies of water. In Texas we have, on average, about 5 feet of evaporation annually in smaller ponds, dugouts and lakes,” Chesser says.

Evaporation causes competition for resources when nutrients and all aquatic life – fish, turtles, frogs, algae, zooplankton – are concentrated in an ever-shrinking body of water. When resources are limited, cyanobacteria have a defense mechanism to ensure their survival: They produce toxins to kill their competition.


Different species of cyanobacteria produce different types of toxins: cytotoxins, which cause vomiting and diarrhea; hepatotoxins, which impact the liver; and neurotoxins, which affect the nervous system. The type of toxin released, quantity ingested, species and size of the animal all impact the severity of injury from ingesting the toxin. Hepatotoxins build up over time, damaging the liver. Neurotoxins affect the ability to breathe and can stop the heart from beating, causing death within a few minutes to a few hours, Chesser notes.

Identifying a problem

If blue-green algae are common in all water bodies, what clues us in on a potential problem in our stock ponds? “The first thing people tend to notice is a paint spill appearance or an oil slick appearance in the water,” Chesser says. While many people see a blue or green color, Chesser cautions us to remember these bacteria occur in many colors and forms.


When resources are limited, cyanobacteria produce toxins to kill off the competition. Photo provided by Brittany Chesser.

“Besides the paint spill or oil slick, people may notice dead fish in the pond,” Chesser says. Fish kills and the spilled paint appearance is often evident in the downwind sections of the water body.

“Without good management practices and careful monitoring of water quality, unfortunately, cattle deaths can occur before ranchers realize there is a problem,” Chesser notes.

Cyanobacteria toxins cause serious consequences in all animals, notes Dr. Jennifer Vrabel of Crete Veterinary Clinic in Crete, Nebraska. Neurological symptoms of cyanotoxin ingestion can occur within 20 minutes of ingestion. “We can see weakness, staggering, pale mucous membranes, difficulty breathing, seizures and death,” she says. “Liver samples obtained during necropsy can confirm toxicity.” If hepatotoxins are present, weakness, bloody diarrhea, photosensitivity and possible liver failure can be seen, but death is less immediate.

Testing options

Taking a water sample, allowing the water to settle overnight and looking to see if "algae" appear on top of the water’s surface or at the bottom of the jar can indicate the presence or absence of cyanobacteria. Cyanobacteria can regulate their buoyancy, unlike true green algae species, and will remain at the top of the jar.


A simple exploratory test is to take a water sample and allow the water to settle overnight to see if the cyanobacteria stay at the top of the jar. Photo provided by Brittany Chesser.

Unfortunately, this jar method isn’t definitive and doesn’t tell you if those bacteria are currently releasing a toxin. Sending a sample to a lab can determine cyanobacteria density and toxin levels, but tests can run into the thousands.

“Any testing is simply a snapshot, telling you only what is happening now – not what has happened or will happen,” she notes. Testing for total levels of nitrogen and phosphorus, which runs about $70, is a reasonably priced test to monitor water. “Cyanobacteria flourish in high-phosphorus environments. Monitoring nutrient levels enables you to be proactive and head off potential problems.”

If you are concerned about cyanobacteria, Chesser recommends acting on your concerns and then implementing measures to prevent nutrient additions and reduce the quantity of cyanobacteria in the water source.

Treatment for cyanobacteria: Better safe than sorry

If concerned about cyanobacteria, the first step is to prevent access to that water source. “Removing the cattle and any other livestock, preventing exposure of pets and people is priority number one,” Chesser cautions. The next step is treatment. Adding fresh water from another source can dilute potential toxins, providing temporary relief, but chemical treatments that kill the bacteria are more reliable and longer-lasting. You should always check with local regulations, Chesser cautions. But effective chemical treatment options can include copper – copper sulfate or chelated copper and sodium carbonate peroxyhydrate. Treatment is cost-effective at about $150 an acre.

If copper products are used to treat cyanobacteria, Vrabel cautions that watering a multispecies herd can be an issue since sheep and goats are more prone to copper toxicity than cattle.

These treatments will reduce the number of cyanobacteria in the water source. However, using these chemicals causes the bacteria to release toxins as they die off. “Animals need to be removed for at least two weeks after treatment,” Chesser emphasizes. Following up treatment with a nutrient binder that makes phosphorus unavailable will help limit the cyanobacteria population. Some standard phosphorus binders include Phoslock, EutroSORB and MetaFloc.

“Contact university or extension personnel to help identify the treatment and best follow-up option best suited to you and your unique circumstances,” Chesser recommends. “But the best route is prevention.”

Management practices that limit cyanobacteria

We can’t control the weather, so we cannot avoid 100% cyanobacteria blooms. However, management practices that limit nutrients in water are vital to ensuring livestock access to safe water. Limiting fertilizer runoff into ponds and not allowing cattle to stand and wade in ponds for extended periods go a long way in limiting cyanobacteria growth.

It only takes 1 pound of phosphorus to equal 500 pounds of algae.

Planning an alternate water source when pastures and paddocks are designed is always a good idea, Chesser says. While she has seen cyanobacteria toxins in water tanks, routine maintenance and cleaning of tanks can prevent problems.

Chesser recommends not fertilizing near ponds or natural drainages and maintaining a 10- to 20-foot vegetative buffer strip around the pond or in areas that experience the most runoff. “In particular, using native plants that naturally take up phosphorus like arrowhead species, American water willows and pickerel weed are great additions to pond edges. And adding large rocks to the pond bottom will make standing in the water uncomfortable for cattle and discourage wading.” Also, limiting access points or excluding cattle from ponds reduces the nutrients introduced to the water that fuel algae and bacteria growth.

Utilizing a range of management practices that limit nutrient additions, particularly phosphorus, to water sources will help prevent cyanobacteria from becoming a problem. But when rain is limited and temperatures are warm, carefully monitor dugouts and ponds for nutrient concentrations and for anything unusual like fish kills, spilled paint or oil slick appearances to help prevent cattle from becoming ill or dying from cyanobacteria toxins.