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WOS:A1997XR96600019; International audience; Hens raised in three different environments were assessed for changes in egg production performance, the rate of incubation behavior expression, and plasma levels of luteinizing hormone (LH) and prolactin for 20 wk following the laying of the first egg. The environments were individual (IFP) or collective floor pens (CFP) and individual battery cages (Cp and Cnp). The hens from three experimental groups (IFP, CFP, and Cp) were transferred from a short (6 h) to a long (14 h) photoperiod, whereas the ones from the remnant (Cnp) were left under a short one. Increase of the photoperiod induced significant increases (P \textless 0.05) in levels of prolactin and LH after I d, and resulted in the onset of egg laying in a delay of 14 d in all groups. However, the overall egg laying performance was highest for the IFP hens. The CFP and IFP hens laid 98 and 24% of their eggs inside the nest boxes, respectively. The hens raised in battery cages did not express incubation behavior, whereas 50 and 33%, respectively, of the CFP and IFP hens did. During the Ist wk of egg laying, levels of prolactin increased for all photostimulated hens but to a greater extent for CFP hens. Higher increases in levels of prolactin were associated with the expression of incubation behavior; however, prolactin levels of nonincubating laying hens were also higher under the CFP treatment. It appears that the rate of expression of incubation behavior, as well as changes in the plasma levels of prolactin and LH throughout an egg production period, are dependent upon rearing conditions in turkey hens.