Optimizing Holstein bovine oocyte development: Evidence-Based donor selection for OPU-IVP

Ovum pick-up and in vitro embryo production (OPU-IVP) in Holstein cows is influenced by donor characteristics, yet quantitative selection criteria for optimizing oocyte developmental competence remain limited. In this study, data from 600 multiparous Holstein cows across three commercial dairy farms were analyzed to evaluate the effects of body condition score (BCS), age, parity, days in milk (DIM), and milk yield on oocyte quality and subsequent embryonic development. Oocyte developmental competence was highest in donors with BCS of 2.75-3.25, age ≤80 months, parity ≤4, and DIM 50-70 days, whereas underconditioned (BCS ≤2.5) or overconditioned cows (BCS ≥3.75), older cows, or those beyond the fourth parity exhibited lower proportions of grade A/B cumulus-oocyte complexes and blastocyst formation. Postpartum interval further affected outcomes, with oocytes collected at 50-70 DIM showing superior maturation, fertilization, cleavage, and blastocyst rates compared with those collected at 30-40 DIM. In contrast, daily, weekly average, or 305-day milk yield did not significantly influence any measure of oocyte developmental competence. These findings indicate that BCS, age, parity, and DIM are key determinants for donor selection in OPU-IVP, and applying these quantitative criteria provides a practical framework for improving embryo production efficiency in commercial Holstein herds.