Twenty one day-old pigs stand in a trailer prior to transport to a nearby weaning-to-market barn at Lehmann Brothers Farms LLC in Strawn, Illinois, U.S. (Daniel Acker/BLOOMBERG)

About 12 years ago, whenever she took a flight somewhere, Temple Grandin would turn her seatmates into impromptu survey subjects. The noted animal scientist showed them two sets of photos: one in which sows were confined in gestation crates and another in which the female pigs roamed in indoor barns. None of the photos were inflammatory or designed to manipulate emotions, she says.

Grandin says two-thirds of the 30 or so people who saw the pictures had “a real problem with gestation crates,” those tightly confining steel cages that often don’t provide enough room for pregnant sows to roll over. “No one in the general public thought it was wonderful,” Grandin says of the crates. Public referendums, she adds, would later confirm her informal survey, as with the 2008 ballot proposition in California where residents voted to ban, among other confinement systems, the gestation crate. The law passed with 63 percent of the vote.

It would appear that corporate America is catching up to public opinion. Since December, a string of fast-food chains, pork producers and other major companies have committed to raising sows without gestation crates or buying meat from suppliers that have dumped the confinement system. It started late last year when Smithfield Foods, the nation’s largest pork producer, announced that 30 percent of its own sows would be moved from gestation crates to group housing by the end of 2011, a sign the company was at last fulfilling a pledge it had made in 2007.

In January, Hormel Foods decided to jump on board, announcing it would convert all of its company-owned farms to group sow housing before 2018. A month later, McDonald’s promised to work with its suppliers to eliminate gestation crates, and two of the fast-food giant’s competitors, Burger King and Wendy’s, soon followed suit. Others have joined the movement this year as well: Denny’s, Safeway and two food-service companies, the Compass Group and Bon Appetit Management.

Participants inside (and outside) the pork and restaurant industries say this seemingly sudden movement against gestation crates actually has been in the works for years, the result of a number of factors. Prime among them, as Grandin indicates, is public opinion. To date, eight states have passed laws prohibiting the crates, including Florida, Arizona, Colorado and Michigan. Some of those laws were approved in public referendums, like California’s, which garnered more than 60 percent of the vote.

“Imagine if a political candidate won with two-thirds of the vote,” says Paul Shapiro, vice president of farm animal protection for the Humane Society of the United States, a major agitator in trying to eliminate gestation crates in the pork industry. “It’s a political slaughter.”

If the public appears dead-set against gestation crates, the scientific and veterinary communities have more mixed feelings.

A 1997 report of the Scientific Veterinary Committee of the European Union — where a gestation crate ban will go into effect next year — noted that because “overall welfare appears to be better when sows are not confined throughout gestation, sows should be preferably be kept in groups.” Likewise in 2008, the Pew Commission on Industrial Farm Animal Production, after 21 / 2 years of research, recommended “the phase-out, within 10 years, of all intensive confinement systems that restrict natural movement and normal behaviors, including swine gestation crates.

But just this year, a U.S. Department of Agriculture report quoted an often-cited 2004 study (itself an aggregation of 35 other studies) that concludes “gestation stalls or well-managed pens generally . . . produced similar states of welfare for pregnant [females] in terms of physiology, behavior performance, and health.”

What’s more, both the American Veterinary Medical Association and the American Association of Swine Veterinarians recognize gestation crates as valid animal husbandry tools, notes Dave Warner, director of communications for the National Pork Producers Council. He says any problems are more about worker training than housing systems.

“If you don’t have the right care given to the animals, they’re going to suffer,” he says. “That’s really the key.”

Warner points out that some of the most horrific acts captured on undercover video by the Humane Society of the United States — the kicking, throwing and punching of pigs and piglets — have nothing to do with gestation crates but are the result of poorly trained workers. He suggests that the Humane Society is conflating the two issues in the public’s mind to help eliminate the crates.

Except that, as Grandin notes, gestation crates are “labor-efficient.” The stalls, she says, “require a less-highly trained person to run them,” which was part of the reason the industry started to embrace the housing system in the 1980s. The crates are typically about 7 feet long and 2 feet wide. They save labor and barn space and prevent sows from doing what they usually do: fight with each other.

Grandin, the animal scientist, acknowledges she has had to reconcile her opinion on gestation crates between two opposing viewpoints: science’s general validation of the system and her own visceral emotions when seeing sows held immobile for years. She says some of those gestation crate studies are too focused on young sows, which haven’t developed pressure sores or repetitive behaviors that indicate stress. “It’s not life,” she says about the confinement. “The way I look at it is: How would you like to live in an airline seat?”

Given Americans’ similar negative feelings, Grandin does give public opinion “some weight” in her distaste for gestation crates. And why shouldn’t she? asks Shapiro of the Humane Society.

“Science can tell you whether you are able to do something, but it doesn’t tell you whether you should do something,” Shapiro says. “There has to be some ethical component to the decision-making.”

There also have to be practical business concerns. An estimated 90 percent of the 6 million sows in the United States are housed in gestation crates, according to informal numbers from the National Pork Producers Council. The aforementioned restaurants and food-service companies couldn’t begin to make promises to buy millions of pounds of gestation crate-free pork without Smithfield’s commitment to changing its sow housing system, suggests Wendy’s spokesman Denny Lynch.

“They supply a lot of the companies that you’re talking about,” Lynch says. The giant pork producer also will likely influence their competitors to embrace a future without gestation crates.

The conversion won’t come cheap. Dennis H. Treacy, executive vice president and chief sustainability officer for Smithfield, notes it will cost $300 million to convert all of the company-owned farms to group housing for sows. A 2010 study by Brian Buhr, professor in applied economics at the University of Minnesota, indicated that it would cost the pork industry between $1.87 billion and $3.24 billion to convert to group housing.

That may explain why there are still some holdouts. Pork producers such as Tyson Foods and Seaboard Foods, so far, have made no commitment. But they are feeling the pressure — not only from the public and animal activists, but from the pork industry itself.

Its own trade magazine, Pork, recently chided recalcitrant companies resisting the call to drop gestation crates. “[I]t’s increasingly apparent,” the magazine editorialized, “that you will lose the battle.”