2026 年 72 巻 4 号 p. 581-589
The dairy industry has seen remarkable increases in milk yield per cow; however, these gains are often offset by declining fertility and a reduced lifespan. This review discusses strategies to enhance lifetime productivity, focusing on three key research areas: 1) Age at first calving (AFC): Retrospective analysis indicates that reducing AFC to < 22.5 months enhances lifetime daily milk yield without adverse effects through the third lactation, provided that the heifer reaches a body weight of ≥ 600 kg before first calving. 2) Double Ovulation: Sequential ultrasonic observation of the ovaries characterizes the pathophysiology of spontaneous double ovulation in high-producing cows during the early postpartum period. Multiparous cows exhibit a higher incidence of double ovulation that leads to twin pregnancies, which is associated with a negative energy balance. This metabolic state can be monitored using milk components such as lactose as a potential metabolic indicator of follicular dynamics. 3) Postpartum uterine health: Diagnostic strategies for endometritis have been optimized. Integrating vaginal discharge scoring and ultrasonography ensures a reliable assessment. This multimodal approach significantly improves the sensitivity of predicting reproductive performance compared to single-method assessments. Improving the lifetime productivity of modern dairy cattle requires precise management across various life stages. Automation and labor-saving technologies, particularly in routine husbandry, reproductive management, and veterinary practices, will become increasingly important for maintaining sustainable dairy operations.
