ULTRASONOGRAPHY

Ultrasonography is a non-invasive imaging technique useful for assessing cattle reproductive function, particularly for monitoring follicle dynamics and ovulation timing [126]. Serial monitoring allows observation of dominant follicle growth during the follicular phase [127]. Delayed ovulation is suspected when a dominant follicle ≥18–25 mm persists for >48–72 h after expected ovulation or estrus without rupture. Other ultrasonographic indicators include increased follicular wall thickness, partial luteinization, and delayed corpus hemorrhagicum formation [128]. Serial scans at 12–24-h intervals enable reliable detection of ovulation by observing the disappearance of the pre-dehiscent follicle and the appearance of the corpus hemorrhagicum [129, 130]. While ultrasonography is highly effective in research and modern herd reproductive management, equipment costs and operator expertise can limit its use in small-scale or resource-limited farms [131].