Dozens of horses dead at historic Elk City ranch

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4. Toxic Additive Found in Feed That Killed 70 Oklahoma Rodeo Horses

Toxic Additive Found in Feed That Killed 70 Oklahoma Rodeo Horses
Preliminary tests show that the feed had been contaminated with Monensin, an additive known to be toxic to horses, Livestock Nutrition Center said.


Riders and horses in a rodeo event, part of a circuit that Beutler and Son Rodeo Company regularly contribute to, in Arlington, Texas, in March. Carolyn Simancik/Getty Images for Teton Ridge

By Christine Hauser
Sept. 3, 2024

The company that supplied the feed that fatally poisoned at least 70 horses at a legacy breeding ranch in Oklahoma last month has confirmed that the shipment had been contaminated with an additive known to be toxic to horses.

Livestock Nutrition Center, which provides custom-blended and premixed feeds to ranches across the United States, said in a statement over the weekend that its “preliminary tests” had shown that a load of feed delivered to Beutler and Son Rodeo Co., in Elk City, Okla., contained Monensin, which can be toxic to horses.

“This likely occurred due to a combination of a failed clean out procedure and a sensor malfunction,” Ronnie Castlebury, the company’s president, said in the statement. He said that it was an “isolated incident to this single load of feed from a single facility” and that no other supplies have been affected, and that the other supplies were safe for animal consumption. … Monensin is an additive that is common in cattle feed but is toxic for horses. The drug is an ionophore, or an antibiotic-like compound.

The company, which has locations in Arkansas, Kansas, Missouri, Texas and Oklahoma, is working with the agriculture departments in Oklahoma and Kansas, the origin source of the feed, to get to the root of the problem, the statement said. Mr. Castlebury could not immediately be reached on Tuesday for comment.

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