Ultrasound sound equipment for pregnancy testing cattle has changed significantly since it became available in the 1990’s. Today’s ultrasound equipment is more portable, more affordable and more adapted to the conditions at the cattle chute.
Let’s start with the “why pregnancy test” question. The most obvious answer is that we want to identify the open unproductive cows so they can be removed from the herd. Let’s slow down here and think this about this more. With ultrasound technology we can collect a lot of useful data by pregnancy testing strategically:
1. We can fetal age the pregnancy to determine if the pregnancy is an A.I. bred and use this information to evaluate the A.I. program.
2. We can fetal age to remove late calving cows and sell or move them to a fall calving herd.
3. We can fetal age to sort cows by cycle to keep calving grounds cleaner.
4. We can monitor bull performance, feeding programs and potential disease problems in a herd.
5. Fetal gender can be determined at some stages of pregnancy and this information is valuable for seedstock production.
The “How” questions can get very interesting. Veterinarians have their preferred type of ultrasound equipment depending on the data that needs to be collected. Each type of ultrasound unit has benefits and some deficiencies. Back in the 1990’s, ultrasound equipment was almost entirely limited to linear rectal probes attached to large modules with built in monitors. This type of equipment required “arm in cow” ultrasound technique at a chute and shade was required to see the monitor outside. Now there are two main probe types and multiple viewing devices available:
1. Linear rectal probes that are used by “arm in cow” method. These probes operate with a higher frequency than convex rectal probes. They produce an image that is smaller and has higher resolution. This better image quality is useful for very early pregnancy testing and for fetal gender determination. Linear rectal probes are useful for examination of ovaries for infertility investigations and for some synchronization programs.
2. Convex rectal probes provide a different type of image and the area scanned inside the cow is considerably larger than a linear probe scan area. This addition scan area is useful for fetal aging at more advanced stages of pregnancy as more of the fetus can be seen. Convex rectal probes work much better with extension arm ultrasound equipment. Extension arm ultrasound is a very good system when larger numbers of cattle need to be pregnancy tested in one day.
3. There has been tremendous progress in viewing devices. The old cathode ray monitors have been replaced with multiple viewing options for ultrasound equipment. Sunlight readable monitors that can be mounted on a chute with Ram Mount® equipment are a game changer that allows for detailed ultrasound examinations in almost any situation. There are direct wired monitors, built in monitors, wireless monitors and now goggles. Goggles also known as head mounted displays are popular with some veterinarians. Caution needs to be used as they are restrictive in their field of view and we know that we need to pay attention while working cattle. Safety first!
One of the most important questions to answer regarding ultrasound pregnancy testing is “When?”. Cattle producers need to understand the basics of cattle reproductive ultrasound so they can work with their veterinarian to achieve the best results. For example, separating A.I. bred heifers from clean-up bull bred heifers can be a relatively easy job or an impossible job depending on the stage of pregnancy. For example, most veterinarians with ultrasound training can separate 50 day A.I. bred heifers from 43 day and under clean-up bull bred heifers with 100% accuracy. Some veterinarians will do this on the extension arm using a convex rectal probe and others will use “arm in cow” linear probe ultrasound for this procedure. However, if the pregnancy testing is delayed until the A.I. heifers are 100 days pregnant and the “gap” is 7 days, errors will likely occur separating these groups. It is quite difficult to accurately separate 100 day pregnancies from 93 day pregnancies as genetics, nutrition, fetal gender, position in the abdomen and other factors are having significant effects on the ability to accurately age the fetuses at this stage.
As the fetus develops in the cow, the ability to age the fetus accurately diminishes. This makes sense because there are so many factors affecting the size of the fetus and the veterinarians ability to reach certain parts of the fetus for a measurement in the large abdominal cavity of a cow.
Fetal aging courses are available to help people develop skills and a better understanding of the processes involved in fetal aging. There are considerable learning resources available online. With a better understanding of fetal aging and the best time during gestation to do test, beef cattle producers and seedstock producers can work with their veterinarians obtain valuable data that can be used to improve cow herds.