AUDIE CORNISH, HOST:
Ninety percent of the eggs we eat come from chickens who live in long rows of wire cages, about eight birds to a cage. Many people like the idea giving chickens more freedom. When these shoppers buy eggs, they look for the label cage-free. That's driving farmers to spend money on new kinds of chicken houses. NPR's Dan Charles went to investigate what life is like for those farmers and their chickens.
DAN CHARLES, BYLINE: In the rolling farmland near Hershey, Pennsylvania, there's a brand-new pair of chicken houses. And inside one of those houses, instead of the standard banks of cages, 18,000 chickens are milling around on the floor. Some are perched on metal bars. A few are madly pecking away at my boots - I have no idea why.
(SOUNDBITE OF CHICKENS FLAPPING AND SQUAWKING)
CHARLES: The chickens just arrived here a few weeks ago. So did the farmer, actually. Harold Sensenig is a young man, newly married.
HAROLD SENSENIG: Oh, been living here for about four weeks now. Moved in a week before the chickens came, got married two weeks before that.
CHARLES: These chickens aren't free-range or organic. They don't get to go outside but they do get to roam around inside the house, so they're cage-free. Sensenig built this kind of chicken house partly because he can get more money for cage-free eggs - twice as much. And the man who's promised to buy them is also here, Paul Sauder, owner of Sauder's Eggs.
PAUL SAUDER: It's the demand that's driving it. I mean, I wouldn't go the risk of paying double the price for these eggs, versus commodity, if I didn't have the demand pushing it on the other side.
CHARLES: Sauder's company will sell these eggs to supermarkets or Aramark, the food service company, or Unilever, which makes Hellman's Mayonnaise. Aramark and Unilever have announced that eventually they'll only buy cage-free eggs.
Doug Balentine, director of nutrition and health for Unilever North America, says when the company announced this plan a few years ago, they couldn't find enough cage-free eggs.
DOUG BALENTINE: There wasn't even enough cage-free egg for us to do Hellman's Light Mayonnaise, initially. And it's going to take us about five years of working with the egg suppliers, so that we can convert all the egg farmers, just to supply the eggs for Hellman's Mayonnaise.
CHARLES: Nationwide, about eight percent of all eggs come from cage-free houses. For Paul Sauder's business it's 10 or 12 percent and growing every year. It's more expensive to produce eggs this way, he says. It takes more space for the same number of chickens because you can't stack them on top of each other. And there's more work involved. Somebody has to walk through the chicken house collecting stray eggs the chickens laid on the ground rather than in their enclosed nests.
But companies like Unilever or Aramark, he says, are responding to consumers who read labels more carefully than ever before.
SAUDER: And the perception that cage-free is a better product than ones from a conventional cage house.
CHARLES: Do you believe it?
SAUDER: From a nutrition standpoint, the egg is the same.
CHARLES: At the same time, he says, there are things he really likes about this kind of chicken house. You're closer to the animals, the way you used to be 40 years ago. And you see more natural chicken behavior - dust-bathing, for instance, or birds perching on long metal rods up near the ceiling.
SAUDER: You come in here at nighttime, those things are all full up there because birds migrate to the top perches because that's where they feel the safest.
(SOUNDBITE OF CHICKENS SQUAWKING)
CHARLES: Whether that means the chickens are really better off, though, still may depend on how you look at it. In Michigan, scientists are carrying out a large-scale experiment with three different chicken houses. One has chickens in traditional cages; one has so-called enriched cages that are bigger and include nests and perches; and a third house is cage-free.
JANICE SWANSON: We have, I think, over 300 cameras mounted within those systems, to be able to collect data.
CHARLES: That's Janice Swanson from Michigan State University, one of the scientists who's in charge of the study. It's funded by egg producers. Swanson says they're measuring everything about each system - how clean the air is; how healthy the chickens are; how much it costs; also, chicken behavior.
On the third floor of the Michigan State Animal Sciences building, students are watching videotapes; counting how often the chickens spread their wings or peck each other. Swanson says they want to measure all these things because there may be tradeoffs between different goals. For instance, in cage-free systems, chicken litter builds up on the floor, so chickens scratch around and dust-bathe in their own waste.
SWANSON: There are concerns about that relative to egg safety. Now, for the hens' behavioral repertoire, this is cool. We can get down and we can dust-bathe, and so on.
CHARLES: The experiment has been running for a year now. Here are some preliminary observations. Hens in cages were cleaner but cage-free chickens kept more of their feathers. Cage-free hens had more freedom, of course, but twice as many of them died during the year.
Swanson says this is just one production cycle. It will take a while longer to draw any firm conclusions.
Dan Charles, NPR News.