The notion of pigs as pets lies at the heart of the animosity between hog producers and their critics, pork producers and some observers say. The question plays into the debate over hog confinements, says DesMoinesRegister.com.

"People think pigs are intelligent, so they have a hard time thinking of them as animals for the slaughterhouse, and they are particularly sensitive to stories about mistreatment of pigs," said Wes Jamison, a former Iowan and Florida communications professor who has written widely on the hog confinement issue.

A group called Mercy for Animals two weeks ago turned over a videotape surreptitiously shot in a Pennsylvania hog confinement showing pigs being euthanised by gassing and being picked up by the ears and sows confined in crates too small for movement. A similar underground tape was shot last year near Coon Rapids.

Daniel Hauff, Mercy's director of investigations, told Fox News: "It's important we look at these animals the same way we look at dogs and cats, because there is no difference. They feel the same pain, the same joy our beloved animals at home do."

That view goes beyond animal rights activists, academics say.

Janice Swanson, director of animal welfare at Michigan State University, warned livestock producers in a speech in Des Moines earlier this year that "polls show that three-quarters of Americans believe animal welfare is as important as low food costs."

"Most urban Americans make a connection between their household pets and farm animals," Ms Swanson said.

"You have people in cities who will spend thousands of dollars for a hip replacement for their dog or cat who think animals that are being raised for slaughter should get the same treatment," said Jamison.

Such a viewpoint has profound implications in the nation's No. 1 hog-producing state, where debate has raged over the move from the traditional open-barnyard environment to industrialised, closed confinements.

Rich Degner, executive director of the Iowa Pork Producers Association, recognises the emotions.

"My wife and son and I had a dog, and when it died I cried right along with them," said Mr Degner, who grew up on a farm in northwest Iowa near Le Mars. "I can assure you that I never shed a tear when any of our pigs went to market."

Professor Jamison and Mr Degner all acknowledge that the friendly, petlike depiction of pigs in movies like "Charlotte's Web," "Babe" and "Winnie the Pooh" have had a major impact on public attitudes toward hogs and their treatment.

"Most of those books and movies are aimed at children, and so they form their opinions at an early age," said Professor Jamison. "People grow up thinking that it's perfectly normal to give a pig a name. They have a hard time handling the idea that the pig is food, even if they like bacon or ham."

But not all hog confinement opponents are pet lovers.

Lisa Morrison of Van Meter grew up on a 160-acre farm near the Jasper/Story County line that was sold in the early 1970s. The farm had cattle and hogs, all raised in the barnyard.

"I never thought of the pigs as pets," she said. "And I don't think pigs are particularly smart, either."

But, she said, "I'm against confinements. Pigs should be able to be outdoors and run around."

In the last year, hog confinements in Iowa and elsewhere have been hit by widely scattered acts of violence, the latest being the suffocation of more than 3,500 hogs in a confinement in Sioux County that authorities said is an act of vandalism.

Joe Anderson, a Nebraska native, received his Ph.D. in agricultural history from Iowa State University and teaches at Mount Royal University in Canada. He has published a history of Midwestern agriculture, "Industrialising the Corn Belt."

He describes the controversy as "a lot of shouting."

"In many ways, animal welfare has never been better. The modern confinements have climate and disease control. But when you concentrate animals together a magnitude of things can go wrong," he said.