The co-owner of a Northern California slaughterhouse who was accused of processing cows with cancer when U.S. livestock inspectors took lunch breaks has pleaded guilty to a federal charge.

Robert Singleton, co-owner of Petaluma-based Rancho Feeding Corp., entered the guilty plea to aiding and abetting in the distribution of adulterated, misbranded and uninspected meat on Friday in a San Francisco courtroom, the San Francisco Chronicle reported.

Singleton is free on $50,000 bail. He signed an agreement that requires him to work with prosecutors who have filed charges against the company’s other owner, Jesse Amaral Jr., and two other employees, Eugene Corda and Felix Cabrera. Those three have pleaded not guilty.

Prosecutors alleged that Singleton and Amaral schemed with employees to slaughter around 80 cows with skin cancer of the eye, instead of stopping plant operations while inspectors took lunch breaks. The government alleges that the plant workers then swapped out the heads of the sick cattle with the heads of healthy cows to hide them from inspectors.

Operations were halted in February after a series of recalls, including one for 8.7 million pounds of beef. The meat was sold at Wal-Mart and other national chains. It was also used in products including Hot Pockets.