In the wake of an ABC News investigation into alleged unsanitary and inhumane practices at one of the nation's largest egg farms, animal rights activists are calling for an end to the egg industry's widespread use of so-called battery cages," in which birds live six to a cage in long stacks of wire cages. "The battery cage system is inherently cruel," said Nathan Runkle of Mercy for Animals, who estimated that 95 percent of the hens used in egg production are kept in battery cages. He urged the industry to adopt more humane methods of egg production, and urged McDonald's, the nation's largest egg buyer, to stop buying eggs from battery cage farms. Undercover video shot by a Mercy for Animals activist who worked at one of the nation's largest egg producers, Sparboe Farms, shows the battery cages in use. "Scott," the activist who made the tape, said that the five to seven birds were kept in each cage, with their beaks cut at an early cage so they wouldn't peck each other, and that each bird lived its life in an area smaller than a standard sheet of paper. He said the birds "can't fully spread their wings, they can't walk around. There were [dead] birds that were left in the cages that were decomposing for weeks or months at a time," claimed Scott. Until the ABC News investigation and the FDA's warning, McDonald's drew all its eggs for restaurants west of the Mississippi River from Sparboe. Just before the ABC News report aired, McDonald's announced that it would no longer get its eggs from Sparboe Farms. Activists, however, are now asking why McDonald's won't stop buying eggs from any producer that uses battery cages.