CHAPTER 40 Ultrasound Determination of Fetal Gender
Fetal gender determination by real-time ultrasound evaluation has become a common reproductive management tool employed by both dairy and beef cow-calf operations. Other benefits of ultrasonography include early pregnancy diagnosis, diagnosis of fetal viability, twins and uterine pathology, and increased accuracy of ovarian structure identification.1–3 When fetal gender determination initially was utilized by beef cattle producers, the payback ratio was estimated to be at least 10:1 and sometimes as high as 100:1.4 It was thought at that time that the high profit margin probably was a result of the newness of the technology and that the procedure would remain profitable even after widespread acceptance. Those predictions have turned out to be accurate, because pregnant beef cows that are marketed with known-gendered fetuses routinely sell for $25 to $50 more per head than contemporaries with unknown fetal gender. Benefits of fetal gender determination for the dairy cow include the increased sale value of pregnant animals carrying heifers, ability to plan embryo transfer programs to fill bull contracts, cull decision information for marginal cows, and ability to predict replacement needs.
To accurately determine fetal gender, it is important that the practitioner have good-quality ultrasound equipment, an excellent understanding of fetal anatomy, and thorough training in reproductive ultrasonography. It also is important for practitioners to recognize the limitations of their ability, and of the technology itself, to ensure producer adoption of fetal gender identification. The reported accuracy of fetal gender determination approaches 100%.5 Under conditions of low light and calm cattle, this accuracy can be realized. Nevertheless, occasionally, despite the practitioner’s best effort, the necessary view cannot be obtained and therefore an accurate diagnosis cannot be made. In such instances it is imperative that the practitioner refrain from guessing; the producer should be informed of the limitations, and the examination be should be repeated in a few days. With experience, nondiagnostic examinations will occur with decreasing frequency.
EQUIPMENT
A number of the ultrasound units available for purchase are more than adequate to identify fetal gender in cattle. Key areas of consideration in purchasing a scanner are image quality, portability, service, and power source.
Console
The console should read at least 64 shades of gray. Most units have 256 shades of gray, but the human eye cannot detect anything greater than 64. The number of channels determines focusing ability. Twelve or more channels are adequate. Beyond 30 channels no visible difference will be noted.6
