Feed mills mixing errors cause monensin toxicity in horses

Traci Eatherton

In October, FDA issued warning letters to two feed mills, Gilman Co-Op Creamery in Gilman, Minn., and Farmers/Ranchers Cooperative Association in Ainsworth, Neb., for feed containing monensin. Monensin is an animal drug approved for use in cattle and poultry that, according to FDA, is highly toxic and potentially lethal to horses, even at relatively low levels. The FDA warning letters come from feed mixed in 2017 according to Farmers/Ranchers Co-op, a business celebrating 101 years. While the feed at Gilman was a special mixed blend according to reports, farmers did not mix monensin in with its blend. Jennifer L. Young, PhD, Farmers/Ranchers consulting nutritionist said the traces found in their feeds were small, and carryover from other grains mixed, showing up at 4.2 parts per million (ppm). Farmers/Ranchers was quick to recall the feeds, and to date, there have been no reports of issues. "We, as an industry, as a whole, have been very careful," Young said. "Studies have shown that horses can ingest a certain amount of monensin without any ill effects." "Of non-target species, horses appear to be the most sensitive to ionophore toxicoses. However, there is a threshold level of exposure in horses below which no adverse effects have been observed. Consumption by horses of a feedlot ration containing 33 ppm of monensin resulted in no evidence of toxicity in horses," according to Elanco, a producer of a monensin product, and a 1996 monensin review. The Gilman case was a little more severe, with the death of multiple horses. According to FDA, the horses consumed feed from a single batch of special-order horse food that was supposed to be non-medicated, be was later found to contain monensin. On June 9 a farm owner in Gilman, Minn., reported that a horse became ill and unable to stand after consuming feed mixed by Gilman Co-Op Creamery, the FDA said in a written statement. Two days later the horse was euthanized. On July 12, two other horses were discovered laying down in their pasture, unable to stand. One horse died that day and the other was discovered dead the following day. Three more horses died over the next month, the FDA said. "The firm did not perform adequate cleanout between batches to remove monensin from the equipment before mixing the horse feed," the FDA said...MORE