May 16, 2012 -- Large numbers of the famed Tennessee Walking Horses have been tortured and beaten in order to make them produce the high-stepping gait that wins championships, an ABC News investigation has found.
"All too often, you have to cheat to win in this sport," said Keith Dane of the Humane Society of the United States.
In the most recent example, an undercover video made by an investigator for the Humane Society documents the cruelty of one of the sport's leading trainers, Jackie McConnell of Collierville, Tennessee.
The video led to a federal grand jury indictment of McConnell and will be seen publicly for the first time tonight on the ABC News program "Nightline."
The tape shows McConnell and his stable hands beating horses with wooden sticks and using electric cattle prods on them as part of a training protocol to make them lift their feet in the pronounced gait judges like to see.
In another scene, McConnell oversees his hands as they apply caustic chemicals to the ankles of the horses and them wrap them with plastic wrap so the chemicals eat into the skin.
"That creates intense pain and then the ankles are wrapped with large metal chains so the horses flinch, or raise their feet even higher," said Dane of the Humane Society.
McConnell is expected to enter a guilty to plea to one count, according to his lawyers.
He declined to comment, or apologize for his acts, when approached by ABC News this week outside his home.
Leaders of the Tennessee Walking Horse industry maintain that such brutality is rare and that trainers do not have to cheat to win championships, which can add millions of dollars to the value of horses.
"They do not have to cheat to win," said Dr. Steve Mullins of the group called SHOW, which oversees inspections of horses before major events. "You don't have to do this kind of junk to win. ... And we are terribly against this stuff."
The industry group maintains that the vast majority of horses are not subjected to the cruel practice of "soring."
But a random inspection by the agents of the Department of Agriculture at last year's annual championship found that 52 of 52 horses tested positive for some sort of foreign substance around front hooves, either to cause pain or to hide it.
Dr. Mullins told ABC News there could be innocent explanations for some of the foreign substances found by the inspectors.