The president of Hallmark/Westland, the US meat firm at the centre of one of the country's largest-ever beef recalls, has admitted that the breach of regulations leading to the recall was an "oversight" that had ruined his company.

During a House Energy and Commerce subcommittee hearing hearing, Steve Mendell was shown a video showing a "downer" cow - that is a cow unable to walk - being forced to slaughter using electric prods and a fork-lift truck.

Mendell said he was shocked and sickened by the video, which was taken secretly at a plant in Chino, California by the Humane Society of the United States. He told the hearing that he did not think the plant would reopen.

Mendell was subpoenaed to appear before the committee on Wednesday (12 March), having previously been summoned to appear in February.

Initially, he had insisted that downer cows had not been processed at the plant but retracted this on being shown the video. "Obviously my system broke down," Mendell said.

The investigation and secret filming of the plant resulted in the recall of some 64.9m kg of beef from Hallmark/Westland, destined for school meals programmes and the fastfood sector.

The Chino plant was not apparently the only casualty of the exposé. The US Department of Agriculture (USDA) was criticised for not uncovering the abuses at the plant sooner, and three officials from the agency have reportedly been placed on administrative leave.

However, Agriculture Undersecretary Richard Raymond pointed out that federal rules do not automatically ban downer cows from being slaughtered and entering the food chain.

The procedure is that, in the event of a cow not being able to walk, processors have to call in USDA vets who then determine if the animal is fit for human consumption.