Robert Singleton, co-owner of the former Rancho Feeding Corp., has pleaded guilty to aiding and abetting in the distribution of adulterated and uninspected beef, reports the San Francisco Chronicle. Singleton, 77, of Petaluma entered a guilty plea before U.S. District Judge Charles Breyer in San Francisco and is free on $50,000 bond.

Singleton signed an agreement requiring him to cooperate with federal prosecutors trying three other defendants with ties to Rancho Feeding Corp. who were indicted last week on charges of conspiracy to distribute the meat. They allegedly had sick cows' heads severed so inspectors couldn't detect the disease.