July 3, 2002

Blue Green Algae Poisoning Threatens Livestock

Several livestock deaths have been attributed to blue green algae poisoning in North Dakota recently, putting livestock producers and veterinarians on alert.

"Typically this is not something we see until the late summer or early fall," says Charlie Stoltenow, veterinarian with the North Dakota State University Extension Service.

Blue green algae, also known as cyanobacteria, typically grows in stagnant warm pond water. When the algae die they produce a toxin that is poisonous to most livestock and wildlife, including ducks, geese, rabbits, muskrats, frogs, fish and snakes.

"In some areas of the state we've already had the right combination of nutrients available, warm water and mild weather for algae blooms to occur," Stoltenow says. Under favorable conditions, blue green algae can double in number in 24 hours and these blooms can turn pond water blue to brownish green.

A close watch for unexplained livestock deaths is important, he notes. Consult a veterinarian to find a cause of death so steps can be taken to prevent additional livestock deaths.

Also, take note of any dead wildlife around bodies of water. The algae flourish only in the top few inches of water so toxic concentrations are typically found only in small ponds where waves don't mix the water thoroughly. Blue green algae blooms don't occur in lakes and rivers.

A veterinarian also can help determine if a particular pond has toxic concentrations of the algae.

If a pond contains toxic concentrations, keep animals from drinking from it by fencing off the water body and providing another source of water. Because the toxins are concentrated at the surface, water may be pumped from the bottom of deep sloughs or potholes to watering tanks.

Typically, toxic algae blooms last only a few days but may persist for several weeks.

"If there are continuing problems, producers may want to consider treating water with copper sulfate or other algicides," Stoltenow advises. "Use them only in ponds that don't drain into other waterways or bodies of water, and don't consume any plants or fish from the pond being treated. Also, because toxin levels increase immediately after treatment, livestock should not be allowed to drink from treated ponds for a week. A recommended treatment rate is two pounds of copper sulfate per acre-foot of water. That's roughly equivalent to eight pounds per million gallons.

For more information on detecting blue green algae and protecting livestock from its toxins, contact your county office of the NDSU Extension Service. Ask for V-1136, "Cyanobacteria (Blue Green Algae) Poisoning."

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Source: Charlie Stoltenow (701) 231-7522, cstolten@ndsuext.nodak.edu 
Editor: Tom Jirik (701) 231-9629 , tjirik@ndsuext.nodak.edu