Comparison of mortality and morbidity rates of calves born from embryo transfer and artificial insemination in Hanwoo cattle

Hanwoo cattle producers have considerable concerns about the higher incidence of perinatal mortality and morbidity in calves derived from in vitro embryo transfer (IVP-ET) than in those derived from artificial insemination (AI). This study aims to compare the mortality and morbidity rates between calves born via IVP-ET and AI in Hanwoo cattle, hypothesizing that calves conceived via IVP-ET will not exhibit higher rates compared to those conceived through AI. This study evaluated a propensity score-matched sample of 310 Hanwoo calves (155 IVP-ET and 155 AI calves) selected from an initial screening pool of 3379 calves born between 2019 and 2022. Matching was performed to control for dam age, parity, dam nursing potential, birth year, and birth season after excluding abortions and stillbirths. Kaplan-Meier survival curves and log-rank tests were used to assess intergroup differences in mortality rates from birth (Day 0) to 6 months of age (Day 180). The cumulative survival rates were 0.929 and 0.936 in the IVP-ET and AI groups, respectively, showing no difference (P = 0.8063). In the IVP-ET and AI groups, the morbidity rates of clinically diagnosed and treated neonatal calf diarrhea (NCD) in preweaned calves were 83.3% and 69.7% (P = 0.0202), and those of bovine respiratory disease (BRD) in postweaned calves were 20.8% and 31.7% (P = 0.0489), respectively. Furthermore, significant linear trends across disease severity levels were observed for both NCD (P = 0.0428) and BRD (P = 0.0446). The odds ratios for NCD and BRD in the IVP-ET vs. AI groups were 2.03 and 0.57, respectively. The two groups showed no differences in mortality rates.