The first farm (farm X), was situated in cen-tral Switzerland at 450 m above sea level. The
henhouse and paddock had been used for >5 yr
before the experiment. The flock of 2,000 layers
was kept in an aviary system (Globogal Voletage
[9]). Groups were separated into 2 larger groups
(Aand B) of 1,000 hens with an additional sepa-ration in the house. During the experiment, this
procedure was tolerated by the certifying bod-ies as an exception from the organic standards
requiring a maximum group size of 500 hens