Algal Blooms Pose Danger to Livestock

Blue-green algae naturally exist in wet places. They thrive in warm, stagnant, nutrient-rich water and are found often in ponds, lakes, and slow moving rivers.

Photo: Wikimedia Commons/Jacques Le Letty

Recent news reports of unsafe drinking water in the Great Lakes area has drawn national attention to toxic algal blooms. In Kentucky, cyanobacteria, also known as blue-green algae, recently were found in Green River Lake, Taylorsville Lake, Barren River Lake, Nolin Reservoir, and Rough River Lake at levels that prompted a recreational advisory.

Algal blooms are accumulated populations of algae in freshwater and marine water environments. They can reduce water quality, causing animals to drink less water than they need to get them through the hot, dry summer. Of the more than 2,000 species of blue-green algae identified, at least 80 are known to produce cyanotoxins (poisons) that can seriously affect animal and human health.

“Although algal blooms can occur at any time of the year, they happen most often in the warmer months of June through September,” said Michelle Arnold, DVM, ruminant veterinarian for the University of Kentucky (UK) College of Agriculture, Food, and Environment. “In freshwater the majority of harmful algal blooms are caused by cyanobacteria.”

Blue-green algae naturally exist in wet places. They thrive in warm, stagnant, nutrient-rich water and are found often in ponds, lakes, and slow moving rivers.

While not all algae are harmful, farm ponds contaminated with fertilizer runoff or direct manure and urine are the perfect environment for toxic blue-green algae. When the weather is hot and dry, rapid algae growth can result in a “bloom,” or a buildup that creates a green, blue-green, white, or brown coloring on the surface of the water. It might even look like a floating layer of paint. If it’s windy, the algal blooms might concentrate along the water’s edge, which increases livestock's risk of ingesting the algae when they come to the pond for a drink.

“Environmental factors such as water temperature, sunlight, water pH, and nutrient concentration all affect when toxins will be produced,” Arnold said. “Cyanotoxins can affect the liver and nervous system and have been implicated in illness and human and livestock death in at least 35 states and in more than 50 countries worldwide.”

Animals that consume affected water can die suddenly or suffer from weakness, staggering, or photosensitization depending on the type of toxin and how much they ingested.

The following simple steps can keep livestock, pets, and humans safe from algae poisoning:

  • Always assume that a blue-green algal bloom is toxic. Provide clean, fresh water to animals, and fence off their access to stagnant, scum-covered ponds.
    “Fencing off natural water sources and providing alternative water sources really is your best option,” said Amanda Gumbert, UKAg extension water quality liaison. “Don’t allow your animals to contaminate the water with feces and urine. Prevent fertilizer or manure runoff from entering water sources. Phosphorus is particularly important in fueling cyanobacteria growth.”
  • If the water source is treated with an algaecide such as copper sulfate, prevent animal access for at least a week to allow any toxins released in the water to degrade. It is best to wait until ponds are no longer stagnant before allowing animals to drink from it.
  • “Creating and maintaining natural buffers, such as trees and shrubs between farmland, housing developments, and waterways can help filter out excess nitrogen and phosphorus before they reach the water,” said Steve Higgins, PhD, director of environmental compliance for the UK Agricultural Experiment Station.
  • To protect yourself, don't swim in water with scum layers or blooms and avoid jet skiing, windsurfing, tubing, or water skiing over scum or blooms. Don’t use untreated water for drinking, cleaning food, or washing camping gear. Boiling water will not remove algal toxins. Thoroughly wash any skin that comes into contact with a bloom. Don’t eat shellfish caught or harvested from a bloom area.
  • Farmers who notice algal blooms in ponds intended for livestock use should have the water tested, as not all algal blooms produce toxins.
    “Many algal blooms in Kentucky are composed of harmless green algae that may look like underwater moss, stringy mats, or floating scum,” Gumbert said. “It is impossible to tell just by looking at the pond if it contains blue-green algae.”

The UK Veterinary Diagnostic Lab can accept water samples and forward them to referral labs to identify blue-green algae and test for toxins.

Visit and search under “Toxicology” for further information regarding sampling and pricing.

“Unfortunately, testing water for an actual toxin is problematic, because toxins are not uniformly distributed in the water source,” Arnold said. “Testing can be quite expensive, and there are many blue-green algae toxins for which no diagnostic tests exist. To be safe, always assume that a blue-green algal bloom has the potential to be toxic.”

For more information, visit the Environmental Protection Agency website

Aimee Nielson is an agricultural communications specialist in UK’s College of Agriculture, Food and Environment.

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