60只75日龄ISA褐蛋鸡随机分成长光组(LL)和短光组(SL), 试验期70 d。短光组恒定光/暗: 8 h/16 h; 长光组起始光/暗: 8 h/16 h, 每周增加0.5 h, 最长光/暗达到13 h/11 h。分别于105和136日龄每组取6羽蛋鸡采样, 观察光周期对蛋鸡GnRH-I mRNA, GnRH-Ra mRNA表达以及卵巢发育的影响。结果表明: 136 d长光组GnRH-I mRNA表达的丰度显著高于短光组(P<0.05), 且极显著高于105 d长光组和短光组的表达(P<0.01)。136 d短光组GnRH-Ra mRNA表达较105 d显著下降(P<0.05), 长光组GnRH-Ra mRNA的表达丰度显著高于短光组(P<0.05)。136 d长光组的卵巢重、卵巢指数极显著高于短光组(P<0.01)。以上说明, 长光明显上调开产前蛋鸡下丘脑GnRH-I mRNA的表达, 促进卵巢的发育; 短光则明显下调垂体GnRH-Ra mRNA的表达, 致使卵巢发育延缓。

60 ISA brown layers at 75 day-old were randomly divided into long light group (LL) and short light group (SL), the experiment lasted 70 days. SL constant light / dark:8 h/16 h; LL set of initial light / dark:8 h/16 h, A weekly increase of 0.5 h, the light / dark reaches 13 h/11 h. Six layers were selected randomly in each group at 105-day-old and 136-day-old respectively to observe the effects of photoperiods on GnRH-I mRNA, GnRH-Ra mRNA expression and ovarian development in layers. The results indicated that GnRH-I mRNA expression abundance in LL was significantly higher than that of SL (P<0.05) the age at the136-day-old, and significantly higher than that of LL and SL (P<0.01) at 105-day-old. The GnRH-Ra mRNA expression in SL at 136-day-old was significantly decreased than that of 105-day-old (P<0.05), the expression abundance of GnRH-Ra mRNA in LL was significantly higher than that of SL (P<0.05). At the136 -day-old, ovary weight, ovary index in LL was significantly higher than that of SL (P<0.01). Therefore, the long photoperiods obviously up-regulated GnRH-I mRNA expression in layers' hypothalamus before start laying, to promote the ovarian development, the short photoperiods significant down-regulation GnRH-Ra mRNA expression in pituitary and cause delay of ovarian development.