Figure 1.

Plasma luteinising hormone concentrations in samples taken prior to death. Hens were exposed to either 1 or 12 days of a long photoperiod (LP) (16:8 hour light/dark cycle) or maintained on a short photoperiod (SP) (8:16 hour light/dark cycle). Open bars represent the samples taken during the light period (4 hours after lights on), whereas the solid bars represent the night samples (4 hours after lights off)