More birds may die in cage-free interior facilities than in more conventional hen-housing. That is one of the results of a three-year long study comparing “conventional cage, enriched colony and cage-free aviary laying hen housing systems and potential impacts on food safety, the environment, hen health and well-being, worker health and safety and food affordability,” as reported by the Coalition for Sustainable Egg Supply. The Coalition, including researchers from Michigan State University, University of California, Davis, Iowa State University, and USDA Agricultural Research Service analyzed each of the five impact areas separately.
The effects on hen health and well-being included:
- Perches were well-used by the hens in both the aviary and enriched colony systems. Nests were also well-used in the enriched colonies, although nest use in the aviary was more variable. Nest pads in both systems stayed clean. Hens in the aviary dust bathed in the litter, whereas in the enriched colony hens used the scratch pad infrequently for dust bathing and foraging; it also became contaminated with manure.
- Pullets reared in the aviary rearing system had better bone quality of the humeri and tibiae, and this was maintained throughout the lay cycle. In contrast, aviary hens had more keel bone damage, which was already evident in aviary-reared pullets. Between 9 and 21% of flights in the aviary ended in failed landings, which could have contributed to the higher level of keel bone breakage.
- There were housing system-related differences in foot health and feather condition, with the enriched colony hens generally having problems intermediate between those of the conventional cage and aviary hens. The most common causes of mortality in all housing systems were egg yolk peritonitis and hypocalcemia. Hypocalcemia was more common in the aviary than conventional cages or enriched colonies and aviary hens that died were more likely to have been caught in the system, cannibalized, or pecked extensively than conventional cage or enriched colony hens.
Like other studies comparing animal husbandry systems, the researchers found that there were positive and negative aspects of each housing system in this study, differentially affecting the birds’ health and welfare, although, notably “[p]hysiological data did not demonstrate the presence of acute or chronic stress in any housing system.”
Logical next steps to insure that each of these housing environments provides for hen health and welfare would be to minimize those features resulting in increased morbidity and mortality and maximize the elements that benefit the hens.
More to come about the potential impacts on food safety, the environment, worker health and safety and food affordability.