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Not AvailableThe objective of this study was to establish the effects of red spectrum of light (650nm, treated n=12) and normal spectrum of light (450nm control=12) on GnRH-I and GnIH mRNA expression, amplitude and frequency of luteinizing hormone (LH) and egg production from 42 to 52 weeks of age in white leghorn hens. Blood samples were collected at weekly interval from both the groups. At the 47th week of age blood samples from both the groups were collected at every 3 h for 36h to study the pulsatile secretion of LH surges. GnRH and GnIH mRNA expression pattern was studied between control and treated birds. Egg production and pause days were calculated between the two groups. LH concentration in the plasma was increased significantly (P<0.01) in hens exposed to red spectrum of light. Plasma LH concentration was higher (P<0.01) in treated birds with more number of LH surges. The amplitude and frequencies of LH were advanced in birds exposed to red spectrum of light during 36 h of sampling at 3h intervals. GnRH-I mRNA concentration was significantly (P<0.01) higher, whereas GnIH mRNA was significantly (P<0.01) lower in birds exposed to red spectrum of light compared to controls. It is hypothesized that exposure of birds to red spectrum of light enhanced (P<0.01) GnRH-I mRNA, along with LH required for ovulation and egg lay. During 77 days (42-52 weeks of age) of the experimental period, egg production was increased (p