Reproductive performance and transcriptome analysis of ovaries at different parities in female rabbits.

ABSTRACT

This study investigated the reproductive performance and ovarian molecular regulation associated with parity in commercial rabbit systems. The pregnancy data of 658 female rabbits from the first to sixth parities (P1 to P6) under the same mating pattern were analyzed, showing a significant decrease in the conception rate in P6. Compared to P1 (N = 120) and P2 (N = 105), P6 (N = 99) had significantly lower performance indices in terms of total litter size, live litter size, survival rate at birth, and weight of 3 and 5 wk old kits (P < 0.05). Using H&E staining, we found that the ovarian primordial follicle reservoir of P6 was significantly lower than that of P1 and P2, and the number of atretic follicles at P6 was significantly higher (P < 0.05). Blood (N = 30 per group) and ovaries (N = 6 per group) in P1, P2, and P6 were collected for measurement of the serum anti-oxidant capacity and indices of ovarian function by ELISA. It was found that serum glutathione, ovarian Klotho protein, and telomeres of P1 and P2 were significantly higher than those of P6 (P < 0.05). The serum levels of ROS and MDA at P1 and P2 were significantly lower than those at P6 (P < 0.05). Additionally, transcriptome analysis showed 213 up-regulated and 747 down-regulated differentially expressed genes (DEGs) between P2 and P6 ovaries. Several DEGs were related to reproduction, including CYP21A2, PTGFR, SGK1, PIK3R6, and SRD5A2. These results demonstrate the influence of parity on reproduction in female rabbits, reflected in a loss of follicle reservoir, disordered levels of anti-oxidants, and indices associated with ovarian function and molecular regulation. This study provides a basis for the strategies to increase reproductive rate in female rabbits.

The pregnancy data of 658 female rabbits from the first to sixth parities (P1 to P6) under the same mating pattern were used to assess the rate of conception at different parities. The reproductive performance and follicular development of P1, P2, and P6 female rabbits were analyzed. The results showed that conception rate was dramatically reduced in P6. Compared with P1 and P2, P6 rabbits showed evidence of lower fertility in terms of total litter size, live litter size, survival rate at birth, and weights of kits at 3 and 5-wk-old. The primordial follicle storage at P6 was significantly reduced, with greater numbers of atretic follicles compared with P1 and P2. In terms of serum glutathione, reactive oxygen species, malondialdehyde, and ovarian Klotho protein, telomeres, the anti-oxidant capacity and ovarian function at P6 was significantly affected by parity. Further, based on the ovarian transcriptomes at P2 and P6, several genes related to reproductive regulation were identified. These findings provide a basis for improving the reproductive rate of female rabbits.