Toxic Weeds Likely Behind the Deaths of 19 BLM Horses

Toxic Weeds Likely Behind the Deaths of 19 BLM Horses

In order to help prevent a similar occurrence in the future, samples of the whorled milkweed will be kept on hand to educate both staff and feed crews.

Photo: George F. Mayfield

The ingestion of whorled milkweed, a highly toxic plant, is suspected to have caused the deaths of 19 horses early last week at the Bureau of Land Management's (BLM) Wild Horse Inmate Program (WHIP) facility in Canon City, according to preliminary laboratory results issued from the Veterinary Diagnostic Lab at Colorado State University.

While final laboratory results are still pending, veterinarians have ruled out any infectious diseases as a possible cause of death. Tests for rabies, equine herpesvirus, and West Nile virus came back negative. All of the deaths occurred in one pen, despite close contact between the horses and those in neighboring pens.

Currently, nine of the horses also in the same pen with similar symptoms are either fully recovered or recovering quickly. As a precaution, animals from pens immediately adjacent to the affected pen will remain at the facility until the final lab results are received, or for an additional three weeks.

With the approval of state animal health authorities, the BLM WHIP facility will resume operations early next week when they begin to ship wild horses and burros that were adopted. These animals were geographically isolated from the affected pen and have been examined by a veterinarian and deemed healthy.

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. This incident suggests that in some cases only small amounts of milkweed need to be consumed to severely affect a group of horses. In order to help prevent a similar occurrence in the future, samples of the whorled milkweed will be kept on hand to educate both staff and feed crews. 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.

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