This survey involved 60 farms including large and small-capacity caged, free-range and non-confined systems. Flocks were evaluated at peak production and before depletion. The study included assessment of behavior, production parameters and measurements of fecal corticosterone as a measure of stress.

The results demonstrated that laying hens are adapted to their housing and showed similar levels of stress irrespective of system.

This study was conducted to determine whether differences occurred from the previous 2004 study which was conducted to draft a NZ Code of Welfare.

The conclusion was that the reviewers were “unable to recommend replacement of current cage systems with alternatives until such time that it could be shown that, in comparison to current cage systems, alternative systems, in the context of supplying New Zealand’s ongoing egg consumption needs, would consistently provide better welfare outcomes for bird and be economically viable.”

This study incorporated a number of considerations which are critical to rational decisions on developing a policy to house egg-production flocks. It was based on a statistical evaluation of objective measurements including corticosterone assay.

Subjective evaluation based on anthropomorphic and emotional approaches, as favored by the opponents of intensive poultry production were rejected. The second consideration related to considering economic viability in establishing national policy. 

In the context of the U.S. providing that farming systems are regarded as acceptable in term of welfare standards based on objective data, individual consumers can be given the choice among eggs produced from different housing systems but they must pay accordingly.