Blue-green algae toxicity more serious during drought
In areas of drought stricken prairie, livestock producers should be vigilant about water testing and visually checking ponds and dams for the presence of blue-green algae. The algae, also called Cyanobacteria, is fatal to livestock.
“Many times, the first sign of trouble is a trail of dead sheep leading away from the dam,” said Dave Ollila, extension sheep field specialist with South Dakota State University. “The poison strikes them so quickly, they will die as they are walking away from the dam.”
Blue-green algae is poisonous to nearly all animals, including cattle, sheep, horses, pigs, dogs, ducks, fish and wild animals. The first sign of poisoning may be the presence of dead wildlife, like snakes and frogs, near the water source.
According to an Extension Extra report issued by South Dakota State University, it is also toxic to humans causing numbness of lips, tingling in finger and toes, and dizziness. Depending upon the species of blue-green algae, it can affect the nervous system or the liver. Animals may die immediately from drinking in the scum, or even hours or days later. Those that do survive will lose weight and become poor doers.
“Livestock affected with the nervous system toxins may show signs including muscle tremors, decreased movement and difficult breathing,” the report explains. “They will collapse and go into convulsions. Animals affected with the liver toxins may show weakness, pale colored mucous membranes, mental derangement, bloody diarrhea, and ultimately death.”
Algae occurs naturally in ponds and stock dams. There are several species, and not all are toxic. Ollila said common problems occur when it is hot and dry and water becomes stagnant. Those conditions stimulate reproduction of the algae through a bloom. The blue-green algae starts out green in color, but will turn blue after it dies and dries on the surface.
Dr. Sandra Holcomb, a veterinarian in Harding (SD) County, said it can be hard to determine if the ponds and dams have toxic water caused by blue-green algae.
“Many times, it depends upon the environmental conditions. The problem is if you have a big enough dam, parts can be good and other parts toxic. I would encourage people to get their water tested before they turn their livestock out, especially this year. It is not going to be a sure thing, but at least you would have some idea whether the water is safe to drink or not – at least the day you test it,” she said.
Typically wind blows algae to one side of the water source, concentrating the toxins and making the water poisonous, Ollila explained.
“A lot of times, it has to do with the wind,” Holcomb concurred. “The water could be bad one day and good the next. Several species of algae are responsible for the toxicity.”
Ollila encourages producers to regularly check ponds and stock dams during the summer. Although water can be tested for the poison, Ollila said typically the bloom only lasts a few weeks and the toxic period may be over by the time the water test comes back. Rain, heavy winds and cooler temperatures can break up the bloom and inhibit growth making it less toxic.
Although blue-green algae toxicity typically occurs in late summer to fall, Ollila urges producers with livestock in areas stricken by drought to be on the lookout much sooner.
“With the hot, dry conditions we are experiencing in some areas, the blooms could come on sooner this year,” he said. “I want producers to be on the lookout for it, rather than being caught off-guard.”
When blue-green algae toxicity does occur, producers may want to consider moving their livestock from that pasture, fence out areas where the toxicity occurs, or use a different water source or pipeline. Copper sulfate can be added to the water as an algacide, if the site has a history of repeated blue-green algae blooms.
“However, it can’t be used to treat the water if you have sheep,” Holcomb stated. “Copper is toxic to sheep. The best thing to do is to fence the dam out or move livestock to another pasture until it rains or conditions are more favorable.”
Ollila said although blue-green algae toxicity is something that occurs every year, it can be a more serious problem when there is a drought because the animals can’t find as many alternative water sources.
“It isn’t something that is talked about a lot, although it can be a real problem,” he said. “People just seem to live with it.”
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