Rancho was ordered to recall 8.7 million pounds of beef after federal government inspectors identified problems at the plant.
One of Amaral Jr.’s partners has testified that some cattle that had cancerous eyes were slaughtered and their meat put into the processing system and that their cancer was covered up by switching heads the government inspectors were checking.
Amaral Jr. is the third person to plead guilty in the conspiracy.
Prosecutors say that for two years, Amaral instructed employees at the slaughterhouse north of San Francisco to process cattle that U.S. Department of Food and Agriculture veterinarians rejected.
The scandal left a lot of ranchers who were purchasing custom slaughter without a place to handle their cattle.