Changes in Ovarian Activity and Expressions of Follicle Development Regulation Factors During the Laying-Incubation Cycle in Magang Geese.

Strong broodiness is an important reproductive characteristic of Magang geese, manifested by periodic laying-incubation activities during the breeding season. To investigate the changes in ovarian activity, follicular development, and gonadal reproductive regulators during the laying-incubation cycle, this study examined ovarian morphology, follicular development, blood reproductive hormones, and the expressions of reproductive regulators in the gonadal stroma, follicular granulosa, and membranous layer of the follicles during the laying, early broodiness, depth of broodiness, and end of broodiness periods of Magang geese. The results showed that ovarian activity degenerated and atrophied with the onset of brooding: the number of LWFs and SYFs decreased rapidly; LFY disappeared; PRL in the blood increased significantly; FSH, P4, E2, and INH decreased significantly; and the mRNA levels of GnIH and steroidogenic factors were up-regulated in the ovarian stroma. With the termination of brooding, the ovarian activity was gradually restored: the numbers of LWFs and SYFs increased gradually; LYF began to appear; PRL in the blood decreased; FSH and E2 increased; P4 remained low; and expressions of GnIH and steroidogenic factors were down-regulated in the ovarian stroma. During the laying period, with the rapid development of follicles, the expressions of FSHR and GnIH were significantly up-regulated; GnIH expression peaked in the SY granulosa layer, while FSHR expression peaked in the F6 granulosa layer. As LYF developed and ovulation occurred, the expressions of FSHR and GnIH were significantly down-regulated, LHR expression was significantly up-regulated, the expression of GnIHR peaked in the F3 granulosa layer and then declined, PRLR expression was the lowest in the F1 granulosa layer, steroidogenic factor StAR was up-regulated, CYP19A1 was down-regulated, and 3β-HSD peaked in the F3 granulosa layer and then declined. The results indicate that GnIH/GnIHR, FSHR, LHR, and PRLR in the gonad correspond to the upstream reproductive hormones and the jointly regulated steroid hormone production and follicular development, which leads to periodic changes in ovarian activity during the laying-incubation cycle of the breeding season of Magang geese. GnIH/GnIHR might play an important regulatory role for FSHR, LHR, and PRLR in the gonads.