Oregon Department of Agriculture (ODA) was notified that several cattle were unexpectedly found dead, likely due to a potential harmful algae bloom in the Cottonwood Reservoir and an increase in toxic plant consumption, Cocklebur.

Harmful Algae Bloom Advisory

Oregon Health Authority (OHA) issued a Harmful Algal Bloom recreational advisory on August 1, 2024, for Cottonwood Reservoir in Harney County. Signs of cyanotoxin exposure in animals include vomiting for companion animals, increased salivation, fatigue, stumbling, shortness of breath, weakness, seizure like activity, liver failure and eventually death. Animals can ingest the toxin through direct exposure to the infected water, eating floating mats or dried crust along the shore. The Center for Disease Control (CDC) is a great resource for photos of what the blooms may look like, but remember, you cannot tell if it is toxic just by looking at it. The link to the general information page for CDC is listed here; page CDC Harmful Algal Blooms.  

Other resources for Harmful Algal Blooms:

• USDA Natural Resources Conservation Service, 
  “How to Protect Livestock from Harmful Algal Blooms”
• AVMA, “Harmful algal Blooms (HABs)” 

We recommend regularly consulting the OHA current advisories website: https://www.oregon.gov/oha/ph/healthyenvironments/recreation/harmfulalgaeblooms/pages/blue-greenalgaeadvisories.aspx

Cocklebur Toxicosis

The receding reservoir levels at Cottonwood Reservoir has led to an increase in growth of the Cocklebur plant. The toxicosis is a resultant from the livestock ingesting the seedling stage of the plant and can be fatal for livestock when consumed via pasture, feed contamination with bur seeds, in hay, or while grazing crop residues. The plant mainly grows in rich soils such as shorelines of ponds and reservoirs. Livestock species are most susceptible to toxicosis in early spring following the germination of seeds and grazing in fields when the plant is young and is highly palatable. The livestock only have to consume about 0.75% of their body weight to cause them to die. The most common signs of the toxicity are depression, weakness, the animal goes off feed, refusal to move, severe spasticity of the muscles, hyperexcitability, unusual walk with the ears erect and the head held high until they are down and no longer able to move.

Additional resource: ODA Spiny Cocklebur