This research was based on the largest to-date analysis of commercial data on egg-laying hen mortality and found that mortality in indoor cage-free housing systems decreases over time as management experience increases and knowledge accrues. The results are published in the journal Scientific Reports.
The analysis included data from 16 countries, 6,040 commercial flocks, and 176 million hens in a variety of caged and cage-free systems. Specifically, the analysis compared mortality of flocks housed in conventional battery cages; furnished cages, which provide hens with additional space, together with a few other comforts such as a perch, nest, and litter substrate; and indoor aviaries, or cage-free housing systems.
The results show that mortality in cage-free flocks is not inherently higher than those housed in conventional battery cage systems but rather declines as managers gain experience and knowledge over time. When comparisons are made between systems with similar levels of technological maturity, mortality is similar in different systems. In fact, the observed trends in the data show that mortality can be lower in cage-free housing if management continues to improve and genetics are optimized for cage-free systems.
It is important to note that lower mortality or longer survival of hens is not necessarily a good indicator of health or welfare. What makes animals suffer is not necessarily what kills them: unhealthy individuals can suffer for extensive periods in caged conditions before succumbing to their fate, if they die at all. However other deaths, such as accidents or predation, may affect otherwise healthy individuals.
These findings are critical for the debate on the welfare of laying hens and on the evolution of the egg industry, which some egg producers have argued would increase hens’ mortality. They also highlight the importance of taking the producer’s degree of maturity and level of experience with a production system into account when conducting any farm animal health, behavior and welfare studies that compare outcomes across systems.
