Comparative superovulation outcomes across estrous phases using PMSG-hCG and rFSH-rhCG in mice

Background Enhancing stimulation efficiency in mice supports the application of assisted reproductive technologies (ART) for species conservation. Objective This study compared the stimulatory potential of two ART-supporting hormone protocols: the conventional PMSG-hCG combination and recombinant gonadotropins (rFSH-rhCG), a newer generation produced by genetic engineering. Methods Sixty-three female mice from four distinct estrous phases were used in this study. Both hormone regimens, with FSH- and LH-like activities, were administered sequentially between 4:00 and 5:00 pm, at a 47–48 h interval. Stimulation success was evaluated based on the proportion of females showing a positive response and the number of oocytes retrieved. Results The diestrus phase yielded the highest response for both treatments. Approximately 60% of the females responded to PMSG-hCG, and 80% responded to recombinant hormones. The number of oocytes recovered reached 239 in the PMSG-hCG group and 137 in the recombinant group. Interestingly, recombinant hormone administration during estrus induced ovulation of 400 oocytes; however, the efficiency ratio was lower than that during diestrus (30.8 vs 34.3). Conclusion Both PMSG-hCG and recombinant gonadotropins effectively stimulate ovulation. The diestrus phase provides the most consistent results; therefore, diestrus is recommended as the optimal stage for superovulation protocols in mice.