Glacier FarmMedia – In over three decades as a veterinarian, Roy Lewis never saw a cow die from ingesting blue-green algae from an infected water source.
But he still says it’s an issue ranchers should watch for.
Blue-green algae can be instantly deadly to an animal that ingests a sufficient amount. However, it’s tricky to identify as the culprit, making it difficult to diagnose as an official cause of death.
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“The toxin dissipates fast, so testing water is often not fruitful and you find nothing following post-mortems of cattle. It is usually diagnosed by ruling out other causes,” said Lewis, a retired large animal veterinarian.
“However, affected cattle are usually found very close to the water source with little sign of struggle, much like water hemlock weed poisoning,” Lewis said.
In a summer that’s seen the high temperatures in which the algae thrives, it’s important to check for it in dugouts and other surface water bodies from which livestock drink, Shawn Elgert writes.
“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,” wrote Elgert, an agricultural water engineer with the Alberta government, in an article on alberta.ca (Dangers of blue-green algae).
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If suspected, contact a water specialist to determine whether it is toxic, wrote Elgert.
“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.”
The good news is that it can be prevented and managed. Aerating the dugout can reduce the chances of algae development, according to 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.”
Wind can push the algae into highly concentrated pockets invisible from the surface, wrote Elgert.
“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.”
Blue-green algae growth depends on nutrients in the water. Buffer strips, grassed waterways and culvert controls are effective tools for reducing nutrients in dugouts. More information is available in the Quality Farm Dugouts manual at open.alberta.ca.
Remote watering is one of the most effective means of keeping nutrients out of water sources. Lewis said this practice alone has reduced the potential of livestock deaths from algae ingestion.
“It was more prevalent years ago with guys watering out of dugouts and sloughs,” he said.
“Now most of them have remote watering set up, so they’ll pump the water that’s deep down in the dugout out to a trough. It’s been shown that if you got good fresh water close by, cattle will drink out of it rather than going to this dugout. So the risk gets less and less.”
An online resource tracks blue-green algae in public water bodies, said Lewis. Hosted by Alberta Health Services, Blue Green Algae Health Advisories posts notices about bodies of water where it has been spotted. The notices can be found at albertahealthservices.ca.
Although focused primarily on preventing human access to the algae, Lewis said it has farm management value as well.
“It helps us in the veterinary world because if you know this lake in this region has a pretty high level of it, you’re going to be more on the lookout for it.”
Other preventive measures are more difficult unless a new dugout is planned. If so, Elgert advises making it deep.
“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,” he said.
He also advised against building dugouts in the waterway. Sediments can bring more nutrients into the dugout and depth can be lost quickly.
The most common method to address blue-green algae is application of a copper product registered for use in farm dugouts. However, it should be used with caution, Elgert noted.
“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 sulphate 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.”
– With files from the Government of Alberta and Roy Lewis, DVM. This article was originally published at the Alberta Farmer Express.
