The effects of reproductive technologies, namely, artificial insemination (AI) and multiple ovulation embryo transfer (MOET), on the production, health, and longevity of Holstein–Friesian cows were evaluated. Data were obtained from the time period between 2017 and 2024 on a Hungarian dairy farm and consisted of 1783 cows (1544 AI and 239 MOET). Deep-frozen semen from identical bulls was used for both the AI and MOET groups. Disease incidence, productive life, and early-lactation milk production phenotypes were collected in these cows. MOET cows demonstrated significantly higher milk yield during the first 100 days of lactation but had a 43.9% greater risk of culling compared with AI cows (p < 0.05). Metabolic and reproductive disorders were the most common reasons for culling cows, with increased frequency of health issues correlating with higher culling risk ratios (p < 0.05). While MOET cows showed lower incidences of metabolic disorders, reproductive problems, and mastitis, their shorter productive lifespan likely limited overall disease exposure. Nevertheless, when MOET cows experienced illness, the impact was more severe, particularly in relation to metabolic issues (p < 0.05). These findings highlight trade-offs between improved genetic potential and health resilience in MOET-derived cows. Despite their higher productivity, their management may require greater health vigilance. This study offers practical insights for dairy producers in selecting reproductive strategies to balance genetic gain, herd health, and longevity under intensive production systems.

Leptin, a hormone primarily produced by adipose tissue, regulates the energy balance, metabolism, and reproductive functions. This review explores leptin's role in calf development from embryogenesis to puberty. Leptin expression is strongly influenced by the nutritional status, with circulating levels dependent on adipose tissue mass and modulated by metabolic hormones such as insulin and glucocorticoids. It plays a regulatory role in the embryonic cell division, adipogenesis, and postnatal energy metabolism. Additionally, leptin modulates appetite, the growth hormone secretion, and the reproductive system maturation. Its presence in the colostrum and milk highlights its significance in the early calf development, influencing the neonatal metabolism and immune function. As calves approach puberty, leptin serves as a key metabolic signal for reproductive maturation. A deeper understanding of leptin’s multifunctional role in calf development could contribute to improved livestock growth and reproductive management strategies.

This study evaluated factors affecting pregnancy outcomes, full-term calving success, and pre-weaning performance following embryo transfer in Holstein–Friesian cattle under commercial farm conditions. A total of 604 in vivo-derived embryos (fresh and frozen–thawed) were transferred into 384 heifers and 220 cows, and pregnancies were diagnosed by ultrasonography. Calves were monitored from birth to weaning. Pregnancy rate per embryo transfer (PR/ET) was higher in heifers than in cows, indicating superior reproductive performance of heifer recipients under field conditions. Recipient corpus luteum (CL) stage II yielded favorable pregnancy outcomes compared to CL stage I, whereas CL stage III comprised a small subgroup (n = 8) exhibiting a descriptive PR/ET of 87.5% that required cautious interpretation due to the limited sample size. Fresh embryos were associated with higher PR/ET than frozen–thawed embryos. Embryo developmental stage did not significantly affect initial pregnancy establishment or full-term calving rates, although stage 6 embryos (blastocyst) showed a non-significant numerical trend toward higher calving rates. Post-diagnosis gestation loss was a primary limiting factor, particularly in multiparous cows. Regarding pre-weaning performance, calves derived from frozen–thawed embryos exhibited a slightly higher birth weights than those from fresh embryos, whereas weaning weight and pre-weaning average daily gain did not differ between embryo types. Overall, recipient category and embryo type are key factors influencing pregnancy success, whereas postnatal performance is less affected. These findings highlight the importance of recipient selection and embryo management strategies for improving reproductive efficiency under commercial dairy farm conditions.