Dietary supplementation of osthole and icariin improves the production performance of laying hens by promoting follicular development.

Osthole (Ost) and icariin (Ica) are extracted from traditional Chinese medicine Cnidium monnieri and Epimedii Folium, respectively, and both exhibit estrogen-like biological activity. This study aimed to determine the efficacy and safety of combining Ost with Ica on the production performance of laying hens and to explore their possible mechanisms. The production performance, egg quality, residues of Ost and Ica in eggs, serum reproductive hormone levels, expression of ovarian reproductive hormone receptor, proliferation of granulosa cells in small yellow follicles (SYF), and progesterone secretion in large yellow follicles (LYF) related genes and proteins expression were detected. The results showed that adding 2 mg/kg Ost + 2 mg/kg Ica to the feed increased the laying rate, average egg weight, Haugh unit, and protein height of laying hens. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and progesterone (P4) levels increased, and the expression of ovarian estrogen receptor (ER), follicle-stimulating hormone receptor (FSHR), and progesterone receptor (PGR) mRNA was up-regulated. Additionally, the mRNA and protein levels of steroidogenesis acute regulatory protein (StAR), cytochrome P450 side-chain cleavage (P450scc), and 3β-hydroxysteroid dehydrogenase (3β-HSD) increased in LYF. Furthermore, mRNA and protein levels of proliferating cell nuclear antigen (PCNA), cyclin E1, and cyclin A2 were up-regulated in SYF. The residues of Ost and Ica in egg samples were not detected by high-performance liquid chromatography (HPLC). In conclusion, dietary supplementation of Ost and Ica increased granulosa cells proliferation in SYF and increased P4 secretion in granulosa cells of LYF, ultimately improving the production performance of laying hens.