Superovulation with eCG alone or combined with the GnRH analogue buserelin improves transferable embryo production in weaned sows without affecting day 6 embryo morphological, cellular, and transcriptomic parameters.

Efficient superovulation protocols are essential to improve efficiency and facilitate scheduling in porcine embryo transfer (ET) programs. Although hCG is widely used to synchronize ovulation following eCG-based superovulation, constraints in its availability have highlighted the need for hCG-free strategies. GnRH agonists could expand ovulation induction options within eCG-based superovulation protocols. In this study, multiparous weaned donor sows received eCG alone (1000 IU, 24 h post-weaning), eCG plus buserelin, a GnRH agonist (10 µg at estrus onset), or no hormonal treatment (control), and embryos were recovered on Day 6 after estrus to evaluate ovulatory response, embryo production efficiency, developmental synchrony, and blastocyst transcriptomic profiles. Both hormonal protocols independently increased ovulatory response by approximately 48% (~37 vs 25 corpora lutea; P < 0.001) and doubled transferable embryo production efficiency compared with controls (P < 0.001), without affecting pregnancy and fertilization rates, embryonic viability, total cell number, or apoptosis. Untreated sows showed the greatest developmental dispersion and a higher proportion of hatched blastocysts, whereas eCG-treated sows showed intermediate variability. The addition of buserelin further improved ovulation-embryo synchrony, with most embryos at the blastocyst stage and all viable embryos classified as transferable. Transcriptomic profiling identified a limited number of differentially expressed genes between treated and control embryos. In conclusion, both hCG-free treatments increased embryo production in weaned sows without adversely affecting the Day-6 blastocyst quality parameters assessed, whereas the addition of buserelin further improved embryo-stage synchrony at collection. Overall, both protocols represent practical hCG-free strategies for in vivo porcine embryo production under commercial conditions.