Source: Government of Alberta
“Blue-green algae is actually cyanobacteria, and can produce toxins that can be dangerous,” says Shawn Elgert, agricultural water engineer with the Alberta government. “It can cause organ damage or even death if ingested by livestock or pets.”
“If you are trying to determine a cause of poisoning, there are other potential toxins on the farm that can also cause harm to cattle such as water hemlock or batteries. You may need to talk to a veterinarian for assistance in determining the cause.”
Elgert says the 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. You should start watching for it when the temperatures rise above 25°C.”
If blue-green algae is suspected in a dugout, it is best to be cautious, says Elgert. “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 you treat it, 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. It is important that cattle do not drink the water during this time so the toxins can degrade. You can follow up with aluminum sulfate and/or hydrated lime treatments afterwards to remove the nutrients from the water to prevent regrowth. Sometimes these coagulant treatments are better than a sole copper treatment.”
Elgert says 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 steeper slopes while avoiding slope deterioration would help make the dugout water cooler.”
Nutrients are required for growth of blue-green algae. “We have information on how to reduce nutrients from entering the dugout in our Quality Farm Dugouts manual. Buffer strips, grassed waterways, culvert controls and off-source watering systems are examples of how you can reduce nutrients.”
Dugouts should not be built in the waterway, as sediments can bring more nutrients into the dugout and depth can be lost quickly, adds 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.”
Elgert also 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.”
