There are 2 main types of reproductive ultrasound on cow calf operations. The first is the traditional “arm in cow” ultrasound that traditionally has been used for early pregnancy diagnosis and fetal aging (less than 120 days) and fetal gender determination in fetuses 58 to 80 days. The second type of reproductive ultrasound is extension arm ultrasound. With ReproScan equipment, this is done with a 4.0 MHz convex rectal probe on the extension arm (ReproArm). With the larger field of view provided by the 4.0 MHz convex rectal probe, more of the fetus can be seen at one time and pregnancy testings and some degree of fetal aging can be done from 30 days and up.
Very early pregnancy tests can be done with “arm in cow” scanning technique starting at approximately 26 days. If clear uterine fluid and a corpus luteum is detected on the same uterine horn, a presumptive diagnosis of pregnant is made. If during these very early checks, a viable embryo or fetus is not detected, the pregnancy should be rechecked. These very early pregnancy examinations should be done with a 6.5 MHz linear rectal probe ultrasound unit such as a BoviScan HD, BoviScan Linear or ReproScan Flexx. Extension arm ultrasound can be started at 30 days of gestation once the scanner has experience.
Fetal aging provides valuable information. Fetal aging can be correlated to calving dates and used to manage heifers and cows at calving. Fetal aging can be used to determine artificial insemination progeny from bull breds. Fetal aging 30 to 120 days can be done with both linear and convex rectal probes. Using the 4.0 MHz convex rectal probe in an extension arm (XTC, BoviScan Curve, ReproScan Flexx and a ReproArm), is a fast and safe way to do this. The 1 cm or 2 cm grid allows for estimated size of fetal structures which can be correlated to the fetal aging charts that ReproScan provides. Most experienced veterinarians use crown rump length to age pregnancies from 28 to 65 days. From 65 to 120 days, head diameter is the most commonly used measurement. Veterinarians often age in 5 day increments from 30 to 80 days and 10 day increments to 120 days. Accuracy is reduced with advanced pregnancies for a multiple of reasons including genetic variation and nutritional affects on the dam.
Cattle pregnancies that are greater than 120 days are more difficult to age accuracy. It is best to use fetal age estimated in months. Some sale barn systems in USA use a trimester system and ReproScan equipment is being used successfully in many of these sale barns.
Fetal sexing is usually done from 58 to 80 days with a 6.5 MHz linear rectal probe such as on the BoviScan HD, BoviScan Linear or ReproScan Flexx. Fetal sexing can be done with the 4.0 MHz convex rectal probe with or without the extension arm. Depending on the type of cattle, sexing fetuses from 70 to 90 days often works out better when using the 4.0 MHz convex rectal probe.