Zhu Huanxi, Chen Zhe, Shao Xibin, Yu Jianning, Wei Chuankun, Dai Zichun, Shi Zhendan
Laboratory of Animal Improvement and Reproduction, Institute of Animal Science, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014 China.
Sunlake Swan Farm, Changzhou, 213101 China.
Front Zool. 2017 Feb 23;14:11. doi: 10.1186/s12983-017-0200-6. eCollection 2017.
The Yangzhou goose is a long-day breeding bird that has been increasingly produced in China. Artificial lighting programs are used for controlling its reproductive activities. This study investigated the regulations of photostimulation and photorefractoriness that govern the onset and cessation of the breeding period.
Increasing the daily photoperiod from 8 to 12 h rapidly stimulated testis development and increased plasma testosterone concentrations, with peak levels being reached 2 months after the photoperiod increase. Subsequently, testicular activities, testicular weight, spermatogenesis, and plasma testosterone concentrations declined steadily and reached to the nadir at 5 months after the 12-hour photoperiod. Throughout the experiment, plasma concentrations of triiodothyronine and thyroxine changed in reciprocal fashions to that of testosterone. The stimulation of reproductive activities caused by the increasing photoperiod was associated with increases in gonadotropin-releasing hormone (GnRH), but decreases in gonadotropin-inhibitory hormone (GnIH) and vasoactive intestinal peptide (VIP) gene messenger RNA (mRNA) levels in the hypothalamus. In the pituitary gland, the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) mRNA abruptly increased during the longer 12-hour photoperiod. The occurrence of photorefractoriness was associated with increased GnIH gene transcription by over 250-fold, together with increased VIP mRNA levels in the hypothalamus, and then prolactin and thyroid-stimulating hormone in the pituitary gland. FSH receptor, LH receptor, and StAR mRNA levels in the testis changed in ways paralleling those of testicular weight and testosterone concentrations.
The seasonal reproductive activities in Yangzhou geese were directly stimulated by a long photoperiod via upregulation of GnRH gene transcription, downregulation of GnIH, VIP gene transcription, and stimulation of gonadotrophin. Development of photorefractoriness was characterized by hyper-regulation of GnIH gene transcription in the hypothalamus, in addition of upregulation of VIP and TRH gene transcription, and that of their receptors, in the pituitary gland.
扬州鹅是一种在中国产量日益增加的长日照繁殖禽类。人工光照程序用于控制其繁殖活动。本研究调查了控制繁殖期开始和结束的光刺激和光不应性的调节机制。
将每日光照时长从8小时增加到12小时可迅速刺激睾丸发育并提高血浆睾酮浓度，在光照时长增加后2个月达到峰值水平。随后，睾丸活动、睾丸重量、精子发生和血浆睾酮浓度稳步下降，并在12小时光照周期后的5个月降至最低点。在整个实验过程中，三碘甲状腺原氨酸和甲状腺素的血浆浓度变化与睾酮相反。光照时长增加引起的繁殖活动刺激与促性腺激素释放激素（GnRH）增加有关，但下丘脑促性腺激素抑制激素（GnIH）和血管活性肠肽（VIP）基因信使核糖核酸（mRNA）水平降低。在垂体中，促卵泡激素（FSH）和促黄体生成素（LH）mRNA水平在较长的12小时光照周期中突然增加。光不应性的发生与GnIH基因转录增加超过250倍有关，同时下丘脑VIP mRNA水平增加，随后垂体中催乳素和促甲状腺激素增加。睾丸中的FSH受体、LH受体和StAR mRNA水平的变化与睾丸重量和睾酮浓度的变化方式平行。
长光照周期通过上调GnRH基因转录、下调GnIH和VIP基因转录以及刺激促性腺激素直接刺激扬州鹅的季节性繁殖活动。光不应性的发展特征是下丘脑GnIH基因转录过度调节，此外垂体中VIP和促甲状腺激素释放激素（TRH）基因转录及其受体上调。
