By Colby Elford, PAg, Livestock and Feed Extension Specialist, Moose Jaw
Dugouts are a great source of water for cattle on pasture. In many cases they provide water to pastures that would otherwise be unusable in the summer. Sometimes, producers are concerned with what they see growing in their dugouts, specifically if the presence of some type of growth will be harmful to their cattle. Therefore, it is crucial to identify what is present so that proper action may be taken.
Duckweed is commonly mistaken as a blue-green algae bloom. It is a free floating plant whose leaves help it sit on the surface of the water. It can be easily identified by its bright green colour and hair-like root that descends below the water's surface. The root can be clearly seen once the plant is removed from the water. Duckweed's disc-like leaves could be described as miniature lily pads.
It is not harmful to cattle and is actually considered beneficial for a dugout. Duckweed forms a thin mat on the surface of the water that prevents light penetration into the water column. At the same time, the roots are drawing nutrients out of the dugout. Both of these functions help to reduce algae and cyanobacteria growth.
If duckweed is what is present in your dugout, no immediate action needs to be taken.
Green algae is also common in Saskatchewan. Our climatic conditions and the nature of our dugouts provide the right combination of nutrients, light, water and temperature for algae to thrive. It also commonly develops in stock tanks and water bowls. Green algae can be identified by scooping some of the bloom out of the water; be sure to wear a rubber glove when doing this. If it is filamentous, like a matt of tangled wet hair and a deeper green than duckweed, it is probably algae. Although green algae is not typically a problem for cattle, it can be a nuisance for water delivery systems. Algae can clog intake lines and filters. To prevent clogging, it is best to have intakes located in the center of the dugout approximately three to four feet below the water’s surface.
Cyanobacteria – Blue-Green Algae
Cyanobacteria is free floating and usually distributed in the top three feet of the water column. Unlike green algae, it will be difficult to pick up out of the water and its appearance can range from looking like a paint spill to grass clippings with a colour that may be green or blueish-green. Some strains of Cyanobacteria are potentially dangerous; in the right conditions some will produce deadly toxins that attack the nervous system and/or the liver.
Cyanobacteria grows rapidly, appearing almost overnight. This is called a bloom. The deadly toxins can also be produced very quickly. When there is a disturbance to the water body causing the bacteria stress, the toxins will be produced and released. Toxin release most commonly occurs because of a wind event that mixes and disturbs the water, causing the cyanobacteria to die and release the toxins. In the case of a wind event, often the cyanobacteria and toxins will be pushed to one end of the water body where the deadly toxin will be further concentrated. When this happens, there is a serious risk to animals that are directly accessing the water and drinking along the shore. Livestock should be prevented from drinking from that water body for 14 days after a bloom occurs to prevent potential death losses.
If cyanobacteria needs to be treated in a dugout, the recommended treatment option is a registered copper sulfate product. It is important to remember that if you decide to treat the water, it will kill the cyanobacteria and cause toxin release. Again, livestock must be removed from the water for 14 days; therefore, an alternative water source must be available. It is also very important to correctly calculate the volume of water present to avoid overtreatment with product. When treating a dugout, it is not recommended to exceed three treatments in one season.
In order to prevent or limit algae and bacteria growth in livestock water sources, there are a couple of things that you can do. Restrict or remove direct livestock access to the water by setting up a remote watering system. This will increase vegetation around the water body which will, in turn, naturally filter nutrients out of runoff water. It will also reduce or eliminate nutrients directly deposited from livestock manure and urine. Funding for projects such as this may be available through the Farm Stewardship Program and the Farm and Ranch Water Infrastructure Program. These programs are offered through the Canadian Agricultural Partnership. Aeration of the dugout or slough is another option that will help to limit algae and bacteria growth and will promote a healthy aquatic ecosystem.
If you have further questions about blue-green algae or other water quality concerns involving livestock, contact the Agriculture Knowledge Centre at 1-866-457-2377, livestock and feed extension specialists are also available.