In letters sent to the companies this week, Chicago-based Mercy for Animals says its undercover videotape at Hy-Line North America's hatchery in Spencer, Iowa, "exposes one of the industry's best-kept secrets — that the egg industry tears male chicks' bodies apart in grinding machines while they are still alive."

The group wants the chains to include a label on egg cartons that says, "Warning: Male chicks are ground up alive by the egg industry." The letters were sent to 50 chains, including Wal-Mart, Whole Foods, Safeway, Harris Teeter and Trader Joe's.

"The violence that you will see is standard and acceptable within the egg industry, and consumers have a right to know about this cruelty so that they can make informed and compassionate purchasing decisions," wrote Mercy for Animals' executive director, Nathan Runkle.

A spokesman for United Egg Producers, a trade group for U.S. egg farmers, called the proposal "almost a joke." Spokesman Mitch Head said Mercy for Animals had no credible authority, as well as questionable motives. "This is a group which espouses no egg consumption by anyone — so that is clearly their motive." The video does in fact end with a call for people to adopt a vegan diet, which eliminates all animal products — meat, eggs or dairy.

Hy-Line said in a statement it has started an investigation "of the entire situation," adding that it would have helped their investigation "had we been aware of the potential violation immediately after it occurred."

The video, shot with a hidden camera and microphone by a Mercy for Animals employee who got a job at the plant in May and June, shows a Hy-Line worker sorting through a conveyor belt of chirping chicks, flipping some of them into a chute like a poker dealer flips cards.

These chicks, which a narrator says are males, are then shown being dropped alive into a grinding machine.

In other parts of the video, a chick is shown dying on the factory floor amid a heap of eggshells after falling through a sorting machine. Another chick, also still alive, is seen lying on the floor after getting scalded by a wash cycle, according to the video narrator.

Hy-Line said the video "appears to show an inappropriate action and violation of our animal welfare policies," referring to chicks on the factory floor.

But the company also noted that "instantaneous euthanasia" — a reference to killing of male chicks by the grinder — is a standard practice supported by the animal veterinary and scientific community.

According to Mercy for Animals, male chicks are of no use to the industry because they can't lay eggs and don't grow large or quickly enough to be raised profitably for meat. That results in the killing of 200 million male chicks a year.

The United Egg Producers confirmed that figure and the practice behind it.

"There is, unfortunately, no way to breed eggs that only produce female hens," said spokesman Head. "If someone has a need for 200 million male chicks, we're happy to provide them to anyone who wants them. But we can find no market, no need."

Using a grinder, Head said, "is the most instantaneous way to euthanize chicks."

There is no federal law that ensures the humane euthanasia of animals on farms or hatcheries, according to Jonathan Lovvorn, vice-president and chief counsel of the Humane Society of the United States.

Hy-Line says on its website that its Iowa facility produces 33.4 million chicks. Based on that figure, Mercy for Animals estimates a similar number of male chicks are killed at the facility each year. Hy-Line did not comment on that estimate.

Runkle, of Mercy for Animals, said most people would be shocked to learn that 200 million chicks are killed a year.

"Is this justifiable just for cheap eggs?" he said.

As to more humane alternatives to disposing of male chicks, Runkle said the whole system is inherently flawed.

"The entire industrial hatchery system subjects these birds to stress, fear and pain from the first day," he said.

© The Associated Press, 2009