The head of the Southern California slaughterhouse at the center of the largest beef recall in U.S. history acknowledged Wednesday that cattle were illegally slaughtered at his plant and that cows too sick to stand were forced into the food supply.

Westland/Hallmark Meat Co. President Steve Mendell made the admissions after a congressional panel forced him to watch undercover video of abuses of cattle at his plant. Mendell watched head-in-hand as cows were dragged by chains, jabbed by forklifts and shocked to get them into the box where they'd be slaughtered.

Afterward he briefly bowed his head, then backed away from claims he made in his written testimony that no ill cows from his plant entered the food supply.

"While these cows should be treated humanely and they were not, these cows were not harvested and they did not enter the food supply," Mendell said in written testimony before the video was demonstrated. "They were not slaughtered, ground or sold. They were euthanized and removed."

The panel's chairman, Rep. Bart Stupak, a Democrat, asked Mendell whether it was logical to conclude from the video that at least two downer cows entered the U.S. food supply.

"That would be logical, yes sir," Mendell said.

"Has your company ever illegally slaughtered, processed, or sold a downer cow?" Stupak asked.

"I didn't think we had sir," Mendell said.

Reminding him that he was appearing under oath, lawmakers asked him why he claimed in written testimony that the abused cows where headed to be euthanized, not for the food supply.

"I had not seen what I saw here today," said Mendell. He said that the Agriculture Department had refused to allow him to see some of the undercover video shot by the Humane Society of the United States.

Stupak pointed out that the video has been posted on the Humane Society Web site.

Mendell's appearance under subpoena before the House Energy and Commerce investigative subcommittee was his first public comment since undercover video of apparent abuses of crippled cattle at his plant led to its shutdown and last month's recall of 143 million pounds of beef. He was a no-show at a committee hearing last month.

Mendell noted that no illnesses have been reported from the recalled beef and the Agriculture Department has found no evidence of problems with it. Some 50 million pounds of the beef went to federal nutrition programs, mostly school lunches.

"I am not aware that there has ever before been a meat recall of this magnitude where there is no evidence of contaminated food and no evidence of any illness," he said.

Mendell said he's received death threats.

"Our company is ruined. We cannot continue," Mendell said. Some 220 employees have lost or are about to lose their jobs, he said.

Two workers shown on the Humane Society video were fired and are facing animal cruelty charges from San Bernardino County prosecutors in an ongoing criminal investigation. Lawmakers have criticized Agriculture Department inspection procedures and called for reform.