Abstract
Real-time ultrasound was successfully applied to predict bovine fetal sex in early preg-nancy. Ultrasound examinations were conducted in 68 cows through 117 trials between days 35 to 93 of pregnancy (day 0 = day of last artificial insemination). Regardless of fetal sex, the genital tubercle was readily recognized as a hyper-echogenic bilobar structure, and each lobe was elon-gated and oval shaped. The tubercle was first identified between the hind limbs on day 45 and then moved towards the umbilical cord in the male, while it moved towards the tail in the female. Thus sex of the fetus was diagnosed by ultrasonography in 90 cases. The diagnosis of sex was not possible in 27 cases: 18 cases with small fetuses before day 52, 2 cases with twin pregnancy, 2 cases with metroptosis after day 80, and 5 cases with maternal obesity. Accuracy of the ultrasonic diagnosis of fetal sex was 93.5% (43/46) for males and 90.9% (40/44) for females. The average umbilical-genital distance in frontal planes was significantly different between male and female fetuses by day 56. In conclusion, ultrasonic examination of the relative location of the genital tubercle was a reliable technique for determining bovine fetal sex between days 56 to 80 of preg-nancy.
