Shoppers in the supermarket today can buy chicken free of nearly everything but adjectives. It comes free-range, cage-free, antibiotic-free, raised on vegetarian feed, organic, even air-chilled.

Coming soon: stress-free?

Two premium chicken producers, Bell & Evans in Pennsylvania and Mary’s Chickens in California, are preparing to switch to a system of killing their birds that they consider more humane. The new system uses carbon dioxide gas to gently render the birds unconscious before they are hung by their feet to have their throats slit, sparing them the potential suffering associated with conventional slaughter methods.

“When you grab a chicken, turn it upside down and put it on the line, it’s stress, stress, stress,” said Scott Sechler, the owner of Bell & Evans. “Our system is designed so that we put them to sleep without stress and we kill them without stress.”

That is sure to appeal to a segment of the chicken-buying public. But telling them about it presents a marketing challenge.