Abstract: The purpose of this experiment was aimed to compare the follicular development and serum steroid metabolism in broiler breeders of different laying weeks. Six broiler breeders were randomly selected at the beginning of preinitiation（24 weeks of age），at the peak of laying（28 weeks of age），and at the late stage of laying（47 weeks of age）. Liquid chromatogram?tandem mass spectrometry（LC?MS/MS）was used to detect serum steroid hormone levels in broiler breeders at different laying weeks of age. The results showed that the number of small yellow follicles was significantly higher at the late stage than those detected at thepeak stage（P<0.01）. The progesterone concentration in the perinatal period was highest，and significantly higher than that in the peak of egg production（P<0.01）. The levelsof 11?deoxycortisol and testosterone were the highest at the peak of egg laying.Meanwhile，the content in the opening perinatal period was the second，and the content in the late laying period was the lowest. Progesterone and estradiol levels were the lowest in the peak laying period but increased in the late laying period. In the late laying period，the content of estradiol was significantly higher than that in the peak laying period（P<0.01），and the level of progesterone was significantly higher than that in the peak laying period（P<0.05）；The level of estradiol in late laying period was significantly higher than that in the opening period（P<0.05）. The content of 17 ? hydroxypregnenolone increased gradually with the increase of laying week age，but there was no significant difference between different weeks of age. Overall，our results indicated that the low reproductive performance of broiler breeders may be related to the retardation of the development of small yellow follicles recruited into the preovulatory hierarchy and the significant increase of estradiol and progesterone in serum.

Key words: Broiler, Laying age, Steroid hormone, Metabolic difference, Liquid chromatography?tandem mass spectrometry

摘要： 该试验旨在研究不同产蛋周龄肉种鸡各级卵泡发育的变化及血清类固醇激素的代 谢差异。随机选择开产期（24周龄），产蛋高峰期（28周龄）及产蛋后期（47周龄）的肉种鸡各6 只，通过液相色谱?串联质谱法（LC?MS/MS）检测不同产蛋周龄肉种鸡血清中类固醇激素水平。 结果表明：与产蛋高峰期相比，产蛋后期肉种鸡卵巢内小黄卵泡数目极显著增加（P<0.01），血 清中孕酮在开产期浓度最高，极显著高于产蛋高峰期（P<0.01）；11?脱氧皮质醇和睾酮的含量 在产蛋高峰期最高；开产期次之，而产蛋后期含量最低；孕酮和雌二醇的水平在产蛋高峰期最 低，而在产蛋后期含量升高；在产蛋后期，雌二醇的含量极显著高于产蛋高峰（P<0.01），孕酮 水平显著高于产蛋高峰期（P<0.05）；雌二醇水平在产蛋后期显著高于开产期（P<0.05）；17?羟基 孕烯醇酮随着产蛋周龄的增加，含量逐步增加，但不同周龄间差异不显著。结果表明产蛋中 后期肉种鸡产蛋量下降可能与小黄卵泡向等级卵泡发育受到阻碍及雌二醇和孕酮水平的显著 增加相关。

关键词: 肉种鸡, 产蛋周龄, 类固醇激素, 代谢差异, 液相色谱?串联质谱