Ovarian transcriptomic analysis and follicular development of Leizhou black duck

This study investigated the factors that caused the differences in egg production during the development of ovarian follicles in Leizhou black ducks. Leizhou black ducks population was divided into 2 groups as high-yield group (HG) and low-yield group (LG). The number of eggs (NE), age at first egg (AFE), weight at first egg, and egg weight (EW) of both groups were recorded, and differences were analyzed using the t test. The logistic model was used to simulate the egg production curves to analyze the production rules. The ovarian follicles of both duck groups were collected to count the number of different grades sized follicles, weigh the ovaries, and observe follicular sections to analyze the developmental differences. Ovarian transcriptomic sequencing was performed to investigate differentially expressed genes and signal pathways in both duck groups. The results revealed a significant difference (P < 0.01) in the NE laid, AFE, and EW between both groups. Comparatively, HG had significantly more (P < 0.01) large yellow follicles (LYF) than LG. The density of medullary layer cells of the follicle section was greater in HG than LG ducks. Transcriptome sequencing revealed a total of 1,027 differentially expressed genes between the HG and LG ducks of which 495 genes were upregulated, and 532 genes were downregulated. Fifty genes were related to reproduction and reproductive processes. Kyoto Encyclopedia of Genes and Genomes-enriched signaling pathways revealed 274 signal pathways enriched in these differentially expressed genes of which the steroid biosynthesis pathway was significantly enriched. Analysis (Q < 0.05) showed that HSD3β → gonadotropin-releasing hormone (GnRH) and estrogen receptor (ESR) → LHβ/ERK1/2 were enriched in the steroid biosynthesis signal pathway. Follicle-stimulating hormone signal pathway mediated by HSD3β → GnRH and ESR → LHβ/ERK1/2 may be involved in ovarian follicle development to regulate LYF reserve process and affect its ovulation cycle, which in turn influence the egg production of Leizhou black ducks.