Influence of metabolic status on oocyte quality and follicular characteristics at different postpartum periods in primiparous rabbit does

Low reproductive performance of high-yield primiparous animals is closely associated with the metabolic stress caused by a simultaneous gestation and lactation. The aim of this work was (1) to analyze body composition and metabolic environment at three time points along lactation (at parturition time; in the lactation period Day 11 postpartum]; and in the postweaning period Day 32 postpartum]) of primiparous rabbit does (Oryctolagus cuniculus) and (2) to investigate the ovarian status at insemination time and the possible link with metabolic environment and with their reproductive performance. To this end, does were either submitted to a semi-intensive reproductive rhythm (Group S, inseminated on Day 11 postpartum) or an extensive rhythm (Group E, inseminated on Day 32 postpartum). Body energy (P < 0.05) and protein content (P < 0.001) as well as serum leptin (P < 0.05) and protein concentrations (P < 0.001) increased significantly along the postpartum period. At parturition, body lipid content was significantly lower and serum nonesterified fatty acids concentrations were significantly higher than that on Days 11 postpartum and 32 postpartum. Concerning ovarian status at insemination time, no significant differences were found in mean follicular stages, serum estradiol, progesterone, and prolactin (PRL) concentrations or in prolactin receptor (PRL-R) immunostaining. However, follicles in Group S showed a significantly higher apoptosis index than that of Group E (P < 0.001). The nuclear and cytoplasmic oocyte maturation rates of Group S were also significantly lower than that in Group E. In addition, conception rate and prolificacy were improved in Group E (P < 0.001 and P < 0.05, respectively). In conclusion, in the early postpartum period, metabolic status seems to impact negatively on ovarian follicle and oocyte quality leading to a poor reproductive outcome in primiparous rabbit does.