Effect of photoperiodic lighting and light color during incubation on egg production, stress and behavioral traits of laying hens

Light exposure during incubation has significant impacts on behavior and welfare in chickens. The aim of this thesis was to investigate if lighting (16L:8D) during whole period (0-21 d) of incubation (LI) using green (520 nm) and white LED as compared with the dark (control) incubation affected productive performance, behavioral and physiological stress responses, and behavior of layer type chickens with special attention to the development of damaging feather pecking behavior. Total of 261 brown layer pullets from two lighted incubation treatments and control (dark incubation) were used in the study. The hens were housed at 12 floor pens in two experimental rooms of the same poultry house giving 2 replicate pens for each treatment in each room (4 pens/treatment). Performance related traits for egg production were recorded for 20 weeks of laying period. Frequency of behaviors were observed at pen levels by scan sampling while all occurrences of feather pecking behaviour and type of pecking were recorded in sampled times at 16, 24, and 32 weeks of age. Stress and fear responses of hens were measured by open field (OF), tonic immobility (TI), manuel restrain (MR) tests and plasma CORT and H:L were measured in blood at different ages. Most prominent result from the study was significantly lower severe and aggressive feather pecking but higher gentle feather pecking acts performed by hens from GREEN incubation lighting as compared to WHITE and CONTROL. Both lighted incubations significantly increased environmental pecking and preening as compared with the CONTROL. Wing-leg stretching was seen more in GREEN than CONTROL and WHITE indicating more comfort behaviour in GREEN. Most sitting was observed in WHITE and while the birds had least sitting frequency in GREEN. Behavioural responses of hens from WHITE, GREEN and CONTROL incubations to TI, MR and OF tests did not indicate a clear differences in sign of fearfulness or anxiety among the groups. However, higher percentage of birds that needs more than one induction per TI in GREEN as compared with WHITE and CONTROL may indicate lower fearfulness in hens from GREEN group. At the end of experiment, feather and comb scoring data indicated that GREEN group had the lowest damage which supported the lower severe feather pecking and aggressive pecking in this group. Blood CORT and H:L ratios did not significantly varied with incubation treatments except CORT levels at 24 wk of age after OF test. At 24 wk, GREEN hens had lower CORT levels than those WHITE and CONTROL hens. The results suggest that lighted incubation with GREEN LED light could be a useful tool to modify pecking behaviour of laying hens, may decrease severe and aggressive pecking, which may improve hen's welfare by reducing stress and anxiety without lowering egg production. However, further investigation is needed to clarify the underlying mechanism.