Nine horses killed by toxic plant

WELLINGTON—Nine horses died after ingesting a toxic plant at a farm in Wellington. The horses were fed hay that had been unknowingly contaminated with the plant. The deaths occurred over a ten day period in early June.
The plant in question is Equisetum, commonly known as horsetail or snap weed. Horses usually will not eat Equisetum and prefer more palatable food, but when it is baled into hay, it is consumed more readily. The plant contains a toxin that inhibits thiamine in the body, causing neurological symptoms leading to collapse and death.
Finding the plant in a hayfield is unusual because it normally grows in wet, sandy or gravelly soil near water. In this instance, the plant had spread heavily into a hayfield and was cut and baled. After eating large amounts of the plant over several days, the horses began to show symptoms. At first the horse would stumble and lose coordination. The symptoms would then worsen until the horses would collapse and die.
The deaths were investigated by Dr. Boyd Thayn and Dr. Dan Harmer at Animal Hospital of Eastern Utah. Multiple samples were collected and sent to a veterinary diagnostic lab for testing. The entire herd was treated with an antidote. Unfortunately, some of the horses symptoms had progressed to the point they did not respond to the treatment.
“As bad as Equisetum is, it’s not even the most toxic plant that grows in Carbon County,” says Dr. Harmer. Before cutting hay or turning animals out on a pasture, Dr. Harmer recommends walking through it and being certain that you know what every plant is.
If you have questions concerning this plant or other dangerous plants in the area please contact your veterinarian or the USU Eastern agriculture extension office.
For more information contact:
Animal Hospital of Eastern Utah
435-637-5797
1989 Airport Rd, Price, UT 84501