Discipline: Veterinary Medicine
The study was conducted to determine structural changes, ultrasound features nnd measurements of the uterus and developing embryo from days 20 to 90 of pregnancy. Four crossbred pregnant dairy cows starting at day 20 post-breeding were used in tho experiment. B-mode ultrasonography of the ovaries was conducted per rectum. Ultrasound densities were classified into hypoechoic, hyperechoic and anechoic. Upon diagnosis of pregnancy, uterine horns were classified into ipsilateral and contralateral sides. Endometrial echotexture was hypoechoic during the early stage of gestation nnd echogenicity increased as the embryonic development progressed. The presence of embryonic fluid in the ipsilateral uterine horn enhanced echogenicity of the surrounding uterine wall as compared to the contralateral uterine horn that contained minimal amount of uterine fluid. Embryonic vesicle and allantoic fluid were first observed on days 27 to 33 of gestation. Allantoic fluid appeared as anechoic structure between the upper and lower uterine wall while amniotic fluids were usually observed between the days 41 to 54 of gestation and appeared as anechoic structure similar to the allantoic fluid. Differences in the time of embryo detection observed could be due to the location of the embryo in the uterus and the location of the uterine horn in the abdomen. Location of the uterus should be considered in pregnancy diagnosis in cattle in addition to the age of the animals since abdominally located uterus at early stage of pregnancy will result to delay in the detection of the embryo.