Equine breeding season is right around the corner. Now is the time to ensure your equipment, protocols, and team are ready for a smooth and successful season. To help you prepare, here are a few practical ultrasound tips and reminders:
Depending on the indication and stage of the reproductive cycle, examinations may be performed transrectally or transabdominally. For most transrectal reproductive exams, a linear probe is preferred. Linear probes provide:
While a curvilinear rectal probe can provide acceptable measurements, the relatively fixed anatomy within the mare’s abdomen makes locating the ovaries and early fetus straightforward without the need for a broader scan field. For clinicians performing a high volume of reproductive work, the improved accuracy of a linear probe outweighs the wider field of view offered by a curvilinear probe.
Prior to any transrectal sonographic examination, thorough evacuation of fecal material from the rectum is essential for optimal image quality and patient safety.
For transabdominal exams in mares, a curvilinear rectal probe or a curvilinear T-handle probe are both appropriate choices. In most cases, clipping is unnecessary unless the mare has a particularly heavy winter coat. Alcohol alone is typically sufficient to achieve adequate probe contact.
Ideally for confirmation of pregnancy, an exam should be done between 16 and 18 days after breeding. At this point, the embryo fixes in place at the base of a uterine horn and will appear to be a circular hypoechoic structure with a hyperechoic rim. This is also the ideal time to identify and eliminate a twin pregnancy. An additional exam should be done at about 1 month of gestation to confirm the pregnancy, as most pregnancies will be terminated in this window.
The next crucial exam is at 6 months to observe fetal viability and placental health; however, many owners may request an exam to sex a foal. Fetal sexing is best done at 60 days of gestation transrectally and is extremely similar to sexing calf fetuses. It can be done after day 90 transabdominally but obtaining an adequate view can be difficult. The 6-month exam should observe a heartbeat and should be able to diagnose any major physical deformity. I