When in a drought situation, thoughts turn immediately to pastures. However water quality can drop off just as quickly during extended periods of hot, dry weather. Water is often the forgotten nutrient. We take it for granted that if there’s water available in the pen or pasture, that the livestock are set.

Following hot, dry, still days, you’ll see ponds, stock dams and a few water tanks with a layer of scum or be completely green in color. This scum/green color is blue-green algae, photosynthetic bacteria also known as cyanobacteria. As the water temperature rises, the cyanobacteria will bloom, causing the noticeable changes. Drought conditions increase the likelihood of a bloom. This year couples low water levels with high temperatures making ideal conditions for cyanobacteria.

Cyanobacterial blooms are harmful to livestock. As the cyanobacteria grow, they store toxins, which are released in the water when they die. There are 2 types of toxins that are associated with blooms, neurotoxin and hepatotoxin. Neurotoxin poisoning is fast acting (15-20 min) and ultimately ends in death. Hepatotoxin (liver) poisoning is much slower acting (a few hours to a day) and is survivable, but the animals will be chronic poor doers. Unfortunately dead animals are often the first sign that there is a problem with cyanobacteria.

Photo from: http://wacf.com

However, the toxins are only half of the problem. This scummy, green water tastes and smells bad, which could cause livestock to avoid water altogether. If this is the only water source, livestock are then facing dehydration. When water intake drops off, so does dry matter intake and it’s a downhill slide with all production.

Fortunately there is a silver lining. There are several practices to prevent cyanobacteria; aeration, aquatic dyes, copper sulfate, straw mats and barley straw to name a few. Contact your local Cooperative Extension Service office for advice on the best prevention plan for your operation.