Breed and Season: Key Determinants of Efficiency in Large-Scale Commercial In Vitro Sheep Embryo Production

The efficiency of the laparoscopic ovum pick-up and in vitro embryo production (LOPU-IVEP) system in sheep is governed by a complex interplay of genetic and environmental factors. This study comprehensively evaluated the effects of breed, season, and their interaction on oocyte retrieval, embryonic development, and pregnancy outcomes in a commercial setting. A 20-month longitudinal analysis of a large commercial cohort revealed that breed was the dominant factor determining oocyte quantity, whereas season exerted a stronger influence on developmental competence. Specifically, autumn and winter provided optimal conditions, resulting in significantly higher cleavage rate and blastocyst rate (p < 0.05). A significant breed-by-season interaction further identified synergistic combinations, such as Black-headed Suffolk in autumn or winter, which achieved superior embryo production outcomes. Importantly, correlation analysis revealed that oocyte quantity was not predictive of developmental potential or pregnancy success. These findings underscore the necessity of a precision management strategy that aligns LOPU schedules with breed-specific seasonal advantages to maximize annual embryo production efficiency.