Optimization of the Embryo Transfer Technique in the Korean Native Cattle: Effects of Key Influencing Factors

The success rate of embryo transfer (ET) is influenced by various factors, including embryo quality, environmental conditions, and recipient cows. This study examines the impact of ET on embryo success rates using embryos produced using the ovum pickup method, with fresh and frozen embryos generated on day 7 after in vitro fertilization and subsequently implanted into recipient cows. The factors that contributed to the success rate of ET were investigated, with a focus on embryo type, parity, and farm management. Furthermore, metabolic profile tests were conducted to determine the factors underlying the observed differences in pregnancy rates across the farms. The analysis revealed that pregnancy rates did not significantly differ according to embryo type or parity. However, significant differences (p < 0.05) were observed in the glucose, cholesterol, non-esterified fatty acid, total protein, globulin, albumin/globulin, and aspartate aminotransferase levels of the recipients. Furthermore, a comparison of farms with high and low pregnancy rates revealed significant differences in the glucose, cholesterol, total protein, albumin, globulin, and albumin/globulin levels (p < 0.05). Differences between farms were associated with the feed management strategy, which highlights the significance of optimal recipient cow management.