Effect of induced molting on ovarian function remodeling in laying hens

Induced molting (IM) can restore the laying rate of aged laying hens to the peak level of laying and rejuvenate ovarian function for the second laying cycle. To explore the mechanism of ovarian function remodeling during IM in laying hens, in this study, ninety 71-wk-old laying lady hens with 60% laying rate and uniform weight were selected for molting induction by fasting. Samples (serum and fresh ovarian tissue) were collected on the day before fasting (F0), the 3rd and 16th days of fasting (F3, F16), and the 6th, 15th, 32nd days of refeeding (R6, R15, and R32), and the number of follicles in each period was counted. Then, the reproductive hormone levels in serum and antioxidant levels in ovarian tissues were detected at different stages, and the gene expression of the KIT-PI3K-PTEN-AKT pathway and GDF-9 in ovaries was measured by qRT-PCR. The results showed that the laying rate increased rapidly after refeeding and returned to the prefasting level by R32. At F16 and R6, the number of mature follicles significantly decreased; the number of primary and secondary follicles significantly increased; the contents of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone (P4) in serum decreased; the relative expression of KIT, PI3K, AKT, and GDF-9 significantly increased; and that of PTEN significantly decreased. At R15 and R32, except for GDF-9, which maintained a high expression state, other indicators showed opposing trends to those observed at F16 and R6. In conclusion, IM activated the KIT-PI3K-PTEN-AKT signaling pathway and promoted the activation of primordial follicles during the fasting period and early resumption of feeding; gonadotropin secretion increased gradually, which promoted the rapid development of primary and secondary follicles to mature follicles and ovulation. This study explained the mechanism of ovarian function remodeling in the process of IM and provided a theoretical basis for improving the ovarian function of laying hens and optimizing the IM program.