Abstract
Background:
The increasing demand for high-quality livestock products necessitates the optimization of reproductive technologies, particularly superovulation and embryo transfer, to enhance genetic improvement and productivity. Superovulation increases embryo availability and accelerates genetic enhancement. The success of these techniques depends on factors such as hormone protocols, donor-recipient selection, and environmental conditions.

Aim:
This study aimed to compared two superovulation protocols—conventional intramuscular injection (P1) and combined epidural-intramuscular injection (P2)—in Wagyu donor cows to evaluate their effects on corpus luteum (CL) formation, embryo yield, and quality.

Methods:
The study was conducted from May to November 2024. Twelve cows were divided into two treatment groups (n = 6 each), with Follicle stimulating hormone administered either through multiple intramuscular injections (P1) or a single-dose epidural-intramuscular injection (P2). Selection criteria included superior genetics, normal reproduction, regular estrus cycles (18–24 days), high fertility, prior calving, and disease-free status. Donor cows had a Body Condition Score of 2.5–3.5, confirmed normal reproductive organs via rectal examination, and were housed in a free-stall system with a controlled diet. Key reproductive parameters, including CL formation, embryo recovery rates (ERRs), and embryo quality, were assessed.

Results:
There were no statistically significant differences between P1 and P2 in CL formation (p = 0.480), ERR (p = 0.810), or embryo quality (p = 0.871). Both protocols supported comparable follicular development, embryo recovery, and transferable embryos across developmental stages (morula, early blastocyst, and blastocyst). While P2 produced slightly more CL and blastocysts, the differences were not significant. Both protocols yielded similar proportions of unsuitable embryos, indicating no adverse effects on fertilization or embryonic viability.

Conclusion:
The findings suggest that the combined epidural intramuscular protocol (P2) is a viable alternative to the conventional intramuscular protocol (P1), offering comparable outcomes while reducing handling stress and labor intensity. Future research should address the pharmacokinetics of hormonal delivery, its long-term reproductive impacts, and its applicability across other breeds to further optimize superovulation strategies for sustainable livestock production and genetic improvement.

Key words: Embryo, Superovulation, Intramuscular, Epidural, Wagyu Cattle