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Hen-housing study finds trade-offs
Cage-free commercial layer house (Photo courtesy University of Georgia Dept. of Poultry Science)
One of the lead researchers on a study comparing housing systems for egg-laying hens says there was no difference in the stress levels of hens in any of the three systems that were tested.
The stress that animals feel in confinement has been one of the big issues in the debate between defenders of modern animal agriculture systems and animal welfare/animal rights activists.
Janice Swanson, director of animal welfare and behavior at Michigan State University, says there was no indication that hens in any of the three systems—cage-free, colony enriched or conventional—experienced acute or chronic stress.
“We measured stress factors and immune factors and so on, and by and large, there was nothing there that indicated that these animals were chronically stressed. None of the housing systems differed from one another in that respect,” Swanson says.
“We’re not all that surprised because measuring stress is very difficult and you have long-term and short-term types of stressor—and, in fact, they’ve never really identified a really good measure for long-term stress—that’s always been the conundrum in terms of that,” she says. “But our measures of stress, overall, did not indicate acute or chronic stress in any of these hens.”
Swanson says the study shows positive and negative impacts and trade-offs associated with each system. For example, while egg-laying hens raised in cage-free systems exhibit a wider range of natural behaviors than more-confined birds, cage-free facilities have higher hen-mortality rates.
“Hens do have pecking orders. They do like to peck and we had hens that were pecked and cannibalized within that (cage-free) system,” Swanson says. “It was one of the major sources of mortality within that system.”
The study also found little difference in egg quality among the three systems. But it did show that the cage-free system—known as the aviary—cost 36 percent more to operate than the conventional system. Costs for the enriched colony system were 13 percent higher than with the small cages.
The research was conducted by the Coalition for Sustainable Egg Supply, which includes animal-health scientists, egg suppliers and major food companies such as McDonalds and Sysco. Animal right advocates have expressed skepticism about the study because of its backing by the egg and food industry.
Swanson says the study was not intended to determine which system is best.
“There’s a lot of things all sides can grab onto there and take a look at,” she says. “It can be confirmatory for those people who want more behavioral freedom for some of those hens. But they also need to recognize that there are issues that do come along with that—and that they need to be properly managed for.”
AUDIO: Janice Swanson
Since we raised free-range poultry for awhile, I see definite advantages to having them in some kind of confinement. Every predator in the Midwest came and had a chicken dinner on our dime. That’s stress for you. With battery cages I could see two or three hens settling their pecking order pretty quickly and then getting down to business.