Latencies (s) to First movement and Righting in the Tonic Immobility test applied immediately after the end of each stress period.

For each stress group (2Wstress: stressed at two weeks of age; 8Wstress: stressed at eight weeks; 17Wstress: stressed at 17 weeks) data are shown in comparison to the non-stressed control chickens tested at the same time. P-values show the significance levels of the Cox’s F-values obtained from survival tests.