Discipline: Veterinary Medicine
The study was conducted to determine structural changes, ultrasound features and measurements of the ovaries from days 20 to 90 of pregnancy. Four crossbred pregnant dairy cows starting at day 20 post breeding were used in the experiment. Bmode ultrasonography of the ovaries was conducted per rectum. Ultrasound densities were classified into hypoechoic, hyperechoic and anechoic. Upon diagnosis of pregnancy, ovaries were classified into ipsilateral and contralateral sides. Presence of wave-like pattern of increase and decrease in the number of subordinate follicles was observed on both ovaries, suggesting the presence of follicular wave development. Dominant follicle appeared as circular anechoic area that was observed in the contralateral ovary of some of the animals on days 27 to 33 of gestation. The corpus luteum appeared as a hypoechoic structure which usually dominates the ipsilateral ovary during the latter part of gestation. Subordinate follicles appeared as small anechoic areas that were usually located near the periphery of the ovary that changed in number during each examination. Both ovaries differ mainly due to the presence of large corpus luteum and several numbers of subordinate follicles and dominant follicle. Ovarian follicular cycle continues even after conception and both ovaries were in different stages of follicular cycle as suggested by different numbers of subordinate follicles during each examination.