“Blue-green algae is actually cyanobacteria, and can produce toxins that can be very dangerous,” says Shawn Elgert, agricultural water engineer with Alberta Agriculture and Forestry. “It can cause organ damage or even death if ingested by livestock or pets.”
“If you are trying to determine the cause of poisoning, there are other potential toxins on the farm that can also cause damage to cattle such as poisonous plants, such as water hemlock.”
Elgert says that first and most important step is to identify the type of growth. Blue-green algae can look like blue-green scum, pea soup or grass clippings suspended in the water. He suggests watching for it when temperatures increase.
If blue-green algae is suspected in a dugout, he says it is best to be cautious.
“You should contact a water specialist to diagnose the growth to determine if it is potentially a toxic growth. You should also remove your livestock from the water source in the interim and prevent them from accessing it. One rule of thumb is that if you can grab it as a solid mass in your hand, it is not blue-green algae.”
If blue-green algae is present, the dugout can be treated using a copper product registered for use in farm dugouts. Once treated, consumption should be restricted for up to a month.
“The use of copper will break the cells open and release the toxins if present into the water all at once,” he explains. “It’s important that you stop using the water during this time so the toxins can degrade. You can follow up with aluminum sulfate and/or hydrated lime treatments afterward to remove nutrients from the water to prevent regrowth.”
He adds that there are also preventative measures that can be taken to try to avoid the problem.
“Temperature is an important factor in the growth of blue-green algae, so a deeper dugout with slopes that are not too flat would help make the dugout water cooler."
Nutrients are required for growth of blue-green algae and information about reducing nutrients from entering the dugout can be found in Quality Farm Dugouts. Nutrients can be reduced by buffer strips and grassed waterways.
“Dugouts should not be built in the waterway, as sediments can bring more nutrients into the dugout and depth can be lost quickly,” explains Elgert. “Aeration of the dugout can also help improve the water quality. A dye packet can also be thrown into the dugout to help prevent photosynthesis from occurring, thereby reducing the growth of blue-green algae. However, one action alone may not be enough to prevent growth.”
He notes that the wind can push the blue-green algae into highly concentrated pockets where the risk of harm is higher.
“Since blue-green algae can rise or fall in the water column, inspection of the dugout should include peering into the deeper part of the water. Always be safe around the dugout by going along with another person and have a rope with a flotation device attached.”
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