19 horses die, 9 others fall ill after eating toxic plant at Colorado facility
The Bureau of Land Management (BLM) reported Friday that preliminary lab results from the Veterinary Diagnostic Laboratory at Colorado State University point to whorled milkweed as being responsible for the deaths of 19 horses and the sickness of nine others.
The toxic plant was found mixed in hay fed to the horses, which were all in one pen.
The BLM began investigating after 11 horses suddenly died Dec. 3 and another eight died the following day. Some of the horses died on their own while others had to be euthanized.
The nine ill horses were said to be fully recovered or recovering quickly.
Pending final test results, veterinarians have ruled out any infectious diseases as a possible cause of death such as rabies, the equine herpes virus and the West Nile virus.
Milkweed is a perennial that often bears blossoms and fruit at the same time but the leaves or any other above-ground parts of the plant are poisonous. They contain several glucosidic substances called cardenolides that are toxic.
It grows in sandy soils on ranges and abandoned farms, along roadsides, in pastures, in ditches, and in waste places.
Milkweed poisoning occurs frequently in sheep and cattle and occasionally in horses.
Most livestock losses are a result of hungry animals being concentrated around milkweed-infested corrals, bed grounds, and driveways. Poisoning also may occur if animals are fed hay containing large amounts of milkweed.
The horses at the Canon City facility are fed approximately 25 tons of hay daily. The hay arrives in 1,000 to 2,000 pound bales.
In order to help prevent a similar occurrence in the future, officials say samples of the whorled milkweed will be kept on hand to educate both staff and feed crews, the bureau said.
Hay vendors will also be advised that hay will not be accepted from suspect areas, such as the edges of fields, along roads and continually wet areas.