Ovary transcriptome profiling in high- and low-yielding Chinese Chahua laying chickens

This study aimed to explore the underlying reasons for the differences in egg production in Chinese Chahua chickens. The Chahua chicken population was divided into two groups, namely a high-yielding group (H) and a low-yielding group (L). The egg-laying performance, ovarian morphology, histological characteristics, and serum hormone concentrations in the H and L groups were analysed. The results revealed that there were significant differences (P < 0.01) between the two groups for the age at the first egg and the number of eggs. The H group showed significantly more (P < 0.01) hierarchical follicles and small yellow follicles than the L group. While several secondary follicles and primary follicles were observed in the ovaries of the H group, only a few secondary follicles were observed in the ovaries of the L group. The serum concentrations of the follicle-stimulating hormone, the luteinising hormone, and oestradiol were significantly higher in the H group compared to that in the L group (P < 0.01). Next, we sequenced and analysed the ovarian expression profiles in the two groups using RNA-seq. The transcriptome sequencing revealed 875 differentially expressed genes (DEGs) between the H and L groups. Of the 875 DEGs, 624 were up-regulated, and 251 were down-regulated. The DEGs were mapped to 31 Gene Ontology (GO) terms and 15 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for the ovarian tissue. The KEGG pathway analysis mainly revealed the involvement of focal adhesion, cytokine-cytokine receptor interaction, and the TGF-beta signalling pathway, while the GO analysis mainly showed involvement of the hormonal activity, extracellular matrix, and extracellular region. Our results showed that understanding the differences in the gene expressions between the ovarian tissues of high- and low-yielding hens may provide a useful reference for improving the egg-laying performance in Chahua chickens.