Cage free eggs are like GMO free popcorn

Cage free eggs are like GMO free popcorn


Yesterday’s announcement that McDonald’s plans to switch to cage-free eggs over the forthcoming decade has generated a lot of discussion about the advantages of various egg farming techniques and trade-offs between systems. Clearly there are some advantages to each system but there didn’t seem to be a definitive answer as to whether cage-free was a superior technique.

Fortunately, thanks to Lara Ginsburg Durban (the Communications Director of the Minnesota Turkey Growers Association), we’ve learned of an extensive research project carried out to measure all these factors, resulting in eight papers published in the journal Poultry Science. The research was carried out at a commercial Midwestern farm by researchers from UC Davis, Michigan State, Iowa State and the USDA.

The researchers evaluated three systems: Conventional Cage (CC) where there are 6 hens per cage, and 80 square inches per hen, and Enhanced Colony Housing system (EC) where there are 160 hens per cage, with 116 square inches per hen, and a Cage Free Aviary system (AV), where the hens could move about freely in a defined space on the floor and on multiple levels, with 144 square inches per bird. Detailed plans for each caging system are shown in this paper.

The researchers carried out parallel studies of the three systems using one flock, divided into the three systems, and repeated then entire experiment with a second flock. Overall, the study and data collection took 3 years.

The final Research Results Report is linked near the top of this summary page, and is a very clear summary of the entire project, in a 42-page downloadable pdf.

So what did they find? To our surprise, chickens did best in conventional cages and worst in the Aviary system on most measurements, although there were some cases were the AV system was best for the birds.  Here’s a summary from the housing system paper.

The aviary pullets cost about $1.85 more per bird than the birds entering the conventional and enriched cage houses. Furthermore, the aviary birds produce about 5% fewer eggs per pullet than the birds in the conventional system. The aviary system begins with the same number of eggs per hen in the initial weeks, but egg production falls much more steeply for the aviary (not shown in the table). Hen mortality is higher in the aviary. By the end of the cycle, the flocks in the aviary system lost 13.3% of the original pullets placed in the barn, compared with 5.2% mortality in the enriched cage system and 4.8% in the conventional system. Also by the end of the cycle, eggs per pullet for the aviary fell to about 10% below the average in the conventional house and 15% below the average in the enriched house.

On the other hand, the hens in the aviary were found to have stronger bones and thus less broken bones than the CC and EC hens, and showed more hen-like behaviors.

There is a really nice interactive chart here, where you can look at the results of the three caging systems on food safety, animal health and well-being, environment, worker health and safety, and food affordability.  AV and EC hens cost a great deal more than CC hens did, AV was worse for worker health and safety, and AV was worse for emissions, and EC the best for ammonia emissions.


According to, McDonald’s decision to require cage-free eggs is certainly a marketing effort based on perceived consumer preference rather than on the extensive published research. And in fact, it will probably drive smaller farmers out of the egg market because of the enormous conversion cost, and higher production cost. Further, farm investments are cyclical, and McDonalds window is probably too small to accommodate the change in caging systems that might take place as old ones need replacement.

In other words, “cage-free” sounds a lot better than it is. Mortality is double that of conventional caging and the cost of egg gathering increases substantially. But, again, it depends on what criteria you choose, as AV hens tend to be stronger and have the opportunity for dust bathing and use of perches.

And what about that popcorn?

popcorn bag1The choice to go to cage-free eggs is a marketing decision, much like the more or less meaningless “GMO Free” labels when there has never been any evidence of harm from transgenic crops. Moreover, there is no such thing as “GMO popcorn”: it simply doesn’t exist. There are really good popcorn poppers to make sure one gets the best popcorn made. But labeling popcorn as non-bag2GMO is catering the food fears of poorly informed consumers rather than being supported by any sort of science. It makes about as much sense as non-GMO salt.


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