Council Directive 1999/74/EC (July 1999) made a distinction between 3 types of rearing systems for laying hens. Of these, the non-enriched cage systems have been prohibited since 1 January 2012. The systems which remain in use are:
enriched cages where laying hens have at least 750 cm² of cage area per hen
alternative systems where the stocking density does not exceed 9 laying hens per m² usable area, with at least one nest for every 7 hens and adequate perches
Whichever system is used, all hens must have a nest, perching space, litter to allow pecking and scratching and unrestricted access to a feed trough.
The directive also states that all egg production units must be registered with the competent authorities in EU countries and have a distinguishing number which can be used to trace eggs back to their farm of origin.
For full details please refer to the directive.
Please refer to the EFSA website for their scientific opinions on the welfare aspects of laying hens.