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

IVP-ET calves face higher neonatal diarrhea risk but lower respiratory disease risk compared to AI calves.

This prospective cohort study compared mortality and morbidity rates between Hanwoo calves conceived via in vitro embryo transfer (IVP-ET) and artificial insemination (AI). From an initial pool of 3,379 calves born between 2019 and 2022, a propensity score-matched sample of 310 calves (155 per group) was selected, controlling for dam age, parity, nursing potential, birth year, and birth season. Abortions and stillbirths were excluded. Kaplan-Meier survival analysis and log-rank testing revealed no statistically significant difference in cumulative survival rates from birth to 6 months of age (IVP-ET: 0.929 vs. AI: 0.936; P=0.8063). However, significant morbidity differences were identified. IVP-ET calves exhibited significantly higher rates of neonatal calf diarrhea (NCD) in the preweaned period (83.3% vs. 69.7%; P=0.0202; OR=2.03), suggesting increased gastrointestinal vulnerability, potentially linked to altered passive immunity transfer or epigenetic dysregulation associated with in vitro culture conditions. Conversely, IVP-ET calves demonstrated significantly lower rates of bovine respiratory disease (BRD) in the postweaned period (20.8% vs. 31.7%; P=0.0489; OR=0.57). Significant linear trends across disease severity levels were observed for both NCD and BRD. These findings indicate that while IVP-ET does not increase overall mortality risk compared to AI, clinicians and producers should implement enhanced monitoring and preventive protocols for NCD in preweaned IVP-ET calves, while BRD risk appears comparatively reduced in this group post-weaning.

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