Abstract: 24 0 dayold male broilers were reared under four light treatments (n=6), white (400760 nm), red (660 nm), green (560 nm) and blue (480 nm) by using LED (lightemitting diodes) as light sources. Light intensity was 15 lx at the height of birds’ heads and scheduled for 23 h of light and 1 h of dark during the entire experiment. Using the method of immunohistochemistry, the distribution and expression of GnRH were shown in different light groups at 49 day of age. The results showed GnRH neurons and fibers were distributed in hypothalamus, thalamus and mesencephalon, and GnRH expression in nucleus preopticus periventricularis (POP), nucleus preopticus medialis (POM), nucleus periventricularis hypothalami (PHN), nucleus paraventricularis magnocellularis (PVN), nucleus ovoidalis (OV) and nucleus rotundus (ROT) in blue light group was higher than those of in red and green light groups. The results suggested that color lights could affect the expression and secretion of GnRH in hypothalamus and thalamus of avian.

Key words: monochromatic light, GnRH, brain, broiler