Histological Characteristics of Follicles, Reproductive Hormones and Transcriptomic Analysis of White King Pigeon Illuminated with Red Light

Red light (RL) has been observed to enhance egg production in pigeons, yet the underlying histological characteristics and molecular mechanisms remain less understood. This study included fifty-four pigeons to assess follicular histology, reproductive hormones, and ovarian transcriptomics on the third day of the laying interval under RL and white light (WL). The results showed that the granulosa cell layer was significantly thicker under RL (<i>p</i> < 0.05), whereas the theca cell and connective tissue layers showed no significant differences (<i>p</i> > 0.05). Higher plasma estradiol (E₂) levels were recorded in the RL group (<i>p</i> < 0.05), as well as follicle stimulating hormone (FSH), although progesterone (P₄) levels were higher under WL (<i>p</i> < 0.05). Moreover, P₄ concentrations in follicle yolk significantly decreased under RL (<i>p</i> < 0.01), with higher FSH and E₂ levels in F1 yolk and similar increases in SF1 yolk (<i>p</i> < 0.01). Transcriptomic analysis revealed 4991 differentially expressed genes in the pigeon ovary. The protein-protein interaction network highlighted genes like <i>HSD11B1</i>, <i>VEGFD</i>, <i>WNT6</i>, <i>SMAD6</i>, and <i>LGR5</i> as potential contributors to hierarchical follicle selection under RL. This research provides new insights into the molecular basis by which RL may promote hierarchical follicle selection and improve egg production in pigeons.