Dressed like storm troopers, with a funny little visor, an odd cable in hand, and a funky battery pack, veterinarians take to the pastures in late summer to ultrasound cows and heifers. This exercise might arouse little more than curiosity for people who have only utilized a traditional preg check via rectal palpation. After all, why do you need fancy equipment to do a job that your arm can do just as well?

That is a good question, and depending on your situation, palpation might be a better fit for your operation. Yet, for producers who want more precision in their cows’ due dates and would like to accomplish the preg checking task sooner in the year, ultrasound may be a better fit.

How it works
Ultrasounding cows is accomplished by emitting ultrasound waves through a probe that is placed in the rectum of the cow. This is the same technology used in human obstetrics; however, it is only available in 2-D. Though external screens are available, most veterinarians use a screen set in a visor that functions like goggles. This way, the veterinarian does not need to cock his or her head in an odd direction while performing the ultrasound procedure.

When the veterinarian examines the ultrasound image, the goal is to identify a live, healthy calf. One benefit that ultrasound has over traditional palpation is that the vet can see the uterine fluid to identify an unhealthy fetus. The vet can also see the calf ’s heartbeat and placental structures.

Once the calf is located, the veterinarian will measure the diameter of the head using a grid present on the ultrasound image. The ultrasound probe is positioned to get the correct view of the head, and then the screen is frozen. The vet can then simply count the number of squares the head occupies on the grid, providing an estimated fetus age measured in days. From the fetus’ age, a due date for the calf is estimated. This procedure is also used in human obstetrics and is accurate when performed correctly. Additionally, the veterinarian can determine the sex of the fetus if the customer desires it.

Considerations if you want to ultrasound your cows
Ultrasounding offers the advantage of detecting pregnancy sooner than regular palpation, at 28 days of age versus the 45 days of age that palpation requires. However, accuracy decreases after the oldest calf is more than 100 days of age. This is due to the variation in calf size. Since ultrasounding functions from a single measurement to calculate the age of the fetus, it assumes that all calves being measured are the same size at the same age. However, as we know from calving, some calves are 60 lbs. when born while others are over 100 lbs. This size variability starts to occur at 100 days of age; hence the accuracy of ultrasounding decreases after that. By 120 days of age, palpation is as, if not more accurate.

Because of this time constraint, the time of year ultrasounding occurs is limited. For most spring-calving herds, this will happen when the cows are out on pasture. This means cows will need to be caught and worked on grass for accurate ultrasounding.

Lastly, because the ultrasound machine is not cheap ($13,000+ is the going rate), ultrasounding typically commands $1-$2 per head more than the cost of traditional palpation. Also, the measuring process involved in ultrasounding means it takes longer to preg check the cattle. Ultrasounding will occur at 66-75% of the speed of palpation.

Is ultrasounding right for my operation?
Many question if the added effort and expense of ultrasounding are justified. Ultimately the best judge for that question is you, as you know the needs of your operation. For some, ultrasounding the heifers is worth it because of the increased likelihood of calving difficulty associated with calving heifers. For others, being able to sort cows accurately by calving date makes life easier in the spring.

One main reason to ultrasound on pasture is drought conditions. When grass is short, a combination of early weaning and ultrasounding to remove the open cows is essential to stretch grass quantity. An open cow is worth less the longer the year goes on. If we can identify and sell her quickly, we will capture more cull value from that sale. This value may exceed the difference in cost between ultrasound and palpation.

Ultrasounding to preg check cows is a good tool that is invaluable for certain producers in certain circumstances. If you can purchase or rent a corral to catch cows on pasture, it may be just the ticket to better profitability for your herd.