High intensity farming practices are in the spotlight after an outbreak of salmonella in the U.S. that was linked with two Iowa farms involved in egg production on a massive scale.

Free range chickens feed in a pasture where Todd Vincent and a partner farm organic chickens near Dawson, Ill. (Seth Perlman/Associated Press)

The outbreak led to the recall of 550 million eggs and forced even supporters of industrialized farming to acknowledge when something goes wrong on a big farm, it will be a big problem

"If you have something go wrong, it'll generally go wrong through a million and a half birds," said Arnold Riebli, one of the owners of Sunrise Farms near of Petaluma, Calif., which has more than a million laying hens.

Athough big farms may end up with big problems, Riebli and others argue that their operations are no more at risk, or are even safer, than smaller farms. Others, such as the Humane Society of the United States, disagree.

The issue has received more attention since two huge Iowa farms acknowledged some of their eggs were contaminated with salmonella and ordered the recall. As many as 1,500 people have become ill in the outbreak, the largest blamed on a single strain of salmonella.

The two Iowa operations, Wright County Egg and Hillandale Farms, house a combined 7.7 million caged hens.

They are among 434 mega-farms, each with at least 100,000 laying hens, that supplied more than three-quarters of eggs in the United States in 2007, the year of the U.S. Department of Agriculture's most recent Census of Agriculture.

Large scale production leads to lower prices

Large-scale production is widely credited with keeping consumer food prices low. When adjusted for inflation, the price of a dozen eggs is less now than in 1980.

Riebli, the chairman of the Association of California Egg Farmers, made the decision to get big long before the 1980s.

"As small farmers we realized that we could not compete in the world as it existed, and we realized that probably 40 years ago," said Riebli.

'Poultry health is a major challenge'—Arnold Riebli, egg producer

It's efficiency that enables a farm to make money — employing one manager, for example, instead of several, and operating one large processing plant. But he acknowledges the potential headaches grew with his farm.

"Poultry health is a major challenge" on a large farm with birds of varying ages, he explained. "Disease is the big problem because you're constantly introducing new birds into the system."

Robert Arnold looks on as his wife, Deanna, holds a rooster on their farm in Garrison, Iowa. The two former workers at Wright County Egg facilities said they reported problems but were ignored. (Charlie Neibergall/Associated Press)

The Humane Society and some others argue farms with hundreds of thousands of caged hens are inherently more at risk.

As evidence, they point to studies done by government health and veterinary agencies in the European Union.

One done in 2004 and 2005 involving more than 450 farms in Great Britain found salmonella enteritis, the variety involved in the recalls, in almost a quarter of farms with 30,000 or more birds. The rate on smaller farms was nine per cent or less, depending on size.

"There are aspects of caged production that are inherently risky, no matter how good the management," said Michael Greger, a physician and the Humane Society's director of public health and animal agriculture.

Some farmers feel the same way. Todd Vincent and a partner have 500 cage-free hens on a farm near Dawson, Ill. He visited a large Iowa farm not involved in the recall and said he wasn't sure how they could keep ahead of problems.

"You've got so many points of entry for disease and other stuff that can happen; you're always looking for that next issue," said Vincent, 40, whose hens regularly spend time in pasture.

Some food safety experts note such research doesn't account for rules the Food and Drug Administration implemented in July, requiring increased testing and inspections of U.S. operations.

Large scale operations have some advantages

"There's no reason to think the (large-farm) birds are any worse off from the salmonella standpoint," said Marion Nestle, a professor of nutrition, food studies and public health at New York University. "If anything, I think the other ones have greater chance of transmission."

One of the chicken confinement sites operated by Wright County Egg in Galt, Iowa, is shown. (Ryan J. Foley/Associated Press)

Caged birds, she explained, are kept off the ground and at least seem less likely to walk around in bacteria-laden feces. Most eggs in the U.S. come from caged hens, regardless of the size of the farm.

Veterinarian Eric Gingerich, who worked with Pennsylvania egg farmers for a decade as part of a job at the University of Pennsylvania, said big farms sometimes even have an edge.

"They usually use more professional managers and they can afford to hire better people," said Gingerich, who now works for a livestock feed company. "Some of the operations hire one person to do just rodent control."

Caroline Smith DeWaal, director of food safety at the Center for Science in the Public Interest, said well-managed farms can be big or small.

"The benefit of buying from a local grower is that if something goes wrong, you go back and you talk to them — you can choose not to buy from them," she said. "Really, it becomes the reputation of the person when you buy directly from the farmer."