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February 10, 2011

Cage Confinement of Laying Hens Increases Salmonella Risk

  • The HSUS' undercover investigations at Iowa egg factories revealed rampant cruelty and food safety problems. The HSUS

An abundance of science shows that forcing hens to endure confinement inside cages increases the risk of Salmonella compared to keeping hens in a cage-free environment.

In fact, there have been sixteen studies published in the last five years comparing caged and cage-free egg operations, and they all found higher rates of Salmonella in the caged facilities.

Even many in the industry agree that cage systems increase Salmonella risk.

The sixteen studies published in the last five years comparing Salmonella rates in cage and cage-free egg facilities:

  • 2010: 20 times greater odds of Salmonella shedding in caged flocks
  • 2010: 7 times greater odds of Salmonella in operations caging hens
  • 2010: 6 times greater odds of Salmonella in operations caging hens
  • 2010: 3 times greater odds in caged hens (though not statistically significant)
  • 2010: More Salmonella-contaminated eggs from caged hens
  • 2009: 35 times greater odds of Salmonella in operations caging hens
  • 2009: 10 times greater odds [PPT] of Salmonella in operations caging hens
  • 2009: 26% greater odds in caged hens (though not statistically significant)
  • 2008: 10 to 20 tiimes greater odds of Salmonella in operations caging hens
  • 2008: 3 times greater odds Salmonella in operations caging hens
  • 2008: 90% greater odds in caged hens (though not statistically significant)
  • 2008: 70% greater odds of Samonella in operations caging hens
  • 2007: 1.8 to 25 times greater odds of Salmonella in operations caging hens
  • 2007: 4.7 times greater odds of Salmonella in operations caging hens
  • 2007: 2.9 times greater odds of Salmonella in operations caging hens
  • 2006: 2.8 times greater odds of Salmonella in operations caging hens


  • The only two studies ever published comparing risk at the consumer level both tied Salmonella infection to cage egg consumption. A prospective case-control study published in the American Journal of Epidemiology found that people who recently ate eggs from caged hens had twice the odds of being sickened by Salmonella, and a study [PDF] in Epidemiology and Infection found nearly 5 times lower odds of Salmonella poisoning in consumers who chose eggs from free-range hens.

    See more:

  • The HSUS' fully-cited white paper on how and why cages increase Salmonella risk [PDF]
  • Conditions uncovered by FDA at egg factories similar to those found by The HSUS in Iowa earlier this year (8/30/10)
  • The HSUS’ new ad campaign accusing the egg industry of playing Russian roulette with Americans’ health (8/27/10) 
  • The HSUS calls on Iowa egg producers to phase out cages in wake of recall (8/19/10)
  • The HSUS calls on egg industry to phase out cages in wake of recall (8/18/10)
  • The HSUS' list of endless eggless options for cruelty-free eating.
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