Equine foetal gender determination in mid- to late gestational mares: A practical inquiry

In recent years, the interest in equine foetal gender determination (FGD) during gestation increased remarkably. Ultrasonographic FGD can be performed in two different periods during gestation. The earliest examination can take place at a gestational age of 60-70 days, whereby the genital tubercle is used to differentiate between male and female foeti. The time window of the second approach is wider (120-210 days), and there are more characteristics to take into consideration. In this article, the feasibility and accuracy of ultrasonographic FGD in mid- to late gestation are evaluated. One hundred twenty-one mares from different breeds with a pregnancy stage between 120 and 270 days were examined once, using B-scale ultrasonography (Esaote MyLab™ClassC). None of the mares were sedated nor shaved, and the procedure was completed within 15 min. Diagnosis was firstly based on the gonads. The final judgement was made based on all visible foetal reproductive organs. In three cases with a pregnancy stage beyond 257 days, FGD was not possible. All of the examined mares in which a FGD could be performed gave birth to a healthy foal. In 98% of the examinations (116/118), the diagnosis was correctly made. In both cases of misdiagnosis, only one characteristic was seen during the procedure and wrongly interpreted. Beyond 210 days of pregnancy, the extremities can preclude a good visualization of the inguinal region. In conclusion, equine FGD in mid- to late gestation is an accessible and accurate technique, although a good ultrasound device is a prerequisite and experience and expertise is necessary.