The FDA is investigating horse feed from a Minnesota co-op after six horses died from eating a single batch of the feed. The feed is believed to contain monensin, an animal drug highly toxic to horses, even at low levels.
On June 9, a farm in Minnesota began feeding its horses feed mixed by Gilman Co-Op Creamery. That evening, one horse became ill and was not able to stand. Two days later, the animal had to be euthanized. On June 12, the owner found two additional horses that were laying down in the pasture that were unable to stand. One died that day and the other was found dead in the pasture the next day, June 13. Over the course of the next month, three more horses died. In total, six horses died after eating the feed containing monensin.
Monensin is an ionophore animal drug approved for use in cattle and poultry feed to increase feed efficiency and prevent coccidial infections. Monensin is highly toxic and potentially lethal to horses though, even at relatively low levels.
The day the batch of horse feed in question was manufactured, Gilman Co-Op Creamery first mixed cattle feed containing monensin. The firm did not perform adequate cleanout between batches to remove monensin from the equipment before mixing the horse feed.
While the feed was a special order for the farm and not distributed to other farms, the FDA is issuing a notice to make feed manufacturers and horse owners aware that monensin in horse feed continues to be a concern.
Horses exposed to monensin may show a range of symptoms including weakness, unsteady gait, inability to get up, diarrhea, abdominal pain, excessive urination, heart failure, or death. Acute toxicity may progress rapidly enough that the horse doesn’t exhibit many symptoms prior to death.
A horse’s reaction to monensin will vary depending on the amount of exposure and the horse’s individual tolerance based on the breed, diet, and metabolism. The horses that consumed the feed from Gilman Co-Op Creamery experienced symptoms and died within 12-48 hours of consuming the feed
The FDA continues to investigate this case and will take action as appropriate to protect animal health.