A management tool used across many cow-calf operations is pregnancy testing, which determines if a heifer or cow is pregnant. Though experts may make different recommendations tailored to individual goals, pregnancy testing can benefit any cow-calf operation.
There are three different primary methods to determine if a female is pregnant early in gestation: rectal palpation, rectal ultrasound and blood test.
Palpation: Immediate Results and Manual Fetal Aging
Rectal palpation is generally done around 45 days to 120 days of pregnancy, Jason Banta, professor and extension beef cattle specialist at the Texas A&M AgriLife Research and Extension Center in Overton, Texas, says. Palpation is valuable because the rancher receives immediate results.
“Another benefit of rectal palpation is if the animal is open, then the technician can feel the [reproductive] tract and feel if there’s anything of concern at that point in time,” Banta says. “A well-experienced technician can do a good job of aging fetuses.”
This method doesn’t always require a technician or veterinarian, but Banta notes that if a rancher does it themselves only once a year, they’re not going to be as confident as somebody who’s doing it on a much more frequent basis.
Of the primary methods, palpation is one of the most physically demanding but can be the most cost-effective. Jason Smith, associate professor and extension beef cattle specialist at the Texas A&M AgriLife High Plains Research and Extension Center in Canyon, Texas, says palpation is not ideal for very early gestation and can be used to estimate fetal age, but is potentially less accurate than ultrasound.
Ultrasound: The Gold Standard for Fetal Sexing and Viability
Rectal ultrasound is typically done 30 days or more after breeding and is performed by a veterinarian or other trained technician using an ultrasound machine and probe to visually evaluate aspects of the reproductive tract and fetus.
Banta clarifies ultrasound technicians doing pregnancy diagnosis are different from those who do marbling and ribeye area ultrasounds. In cattle, a rectal ultrasound is necessary versus external ultrasound used on some small ruminants.
This method also provides immediate results and is considered the most accurate for sexing and aging the fetus.
“This, in my opinion, is considered by most to be the gold-standard method of early pregnancy determination,” Smith explains. “Ultrasound can also be used to identify twins, detect the fetal heartbeat, or otherwise identify embryonic mortality, or cows that have recently aborted, resorbed their pregnancy, or have pregnancies that are no longer viable.”
While the ultrasound method is more expensive because of the ultrasonography equipment, it may be less physically demanding and less of a safety risk to the technician when compared to palpation if using a wand to hold the probe, Smith continues.
“In some situations, producers would purchase that equipment and do it themselves, but that’s more of an exception than the rule,” Banta says.
Another consideration is the facilities needed to properly use equipment.
“It may need to be conducted in an area where it will not be exposed to rain or snow, and therefore may require more facility infrastructure or cattle movement,” Smith adds.
Blood Testing: Convenient, Chute-Side and Producer-Friendly
Blood tests can be done 25 to 28 days post-breeding depending on the test type. This method does not require a technician and is something the rancher can do on their own.
“One of the nice things about blood test is it’s very easy for people to learn how to draw blood out of the tail vein,” Banta explains. “Then they can take the blood from the blood test and either send that to the lab and you have it analyzed or there are some chute-side tests.”
A blood sample is collected and assayed to determine the presence of pregnancy-associated glycoproteins (PAGs) or pregnancy-specific protein B. Specific examples of some of the commercially available test products include BioPRYN, Alertys, Pregnostx and DG29, Smith says.
Sending a test like BioPRYN, manufactured by BioTracking, is usually considered a non-invasive alternative to other methods. Neogen is a certified satellite lab for BioTracking and says that results are available the day after samples are received in the mail.
“These are highly accurate at identifying open females if samples are labeled with the correct animal’s ID, do not get cross-contaminated, and are collected the necessary number of days following breeding and calving,” Smith says.
There are guidelines requiring that the animal be at least 60 to 90 days post-calving depending on the test. Taking blood samples too soon after calving or too early after breeding may result in false results.
“While they are simple, economical, and useful, they do not provide insight into other aspects of the pregnancy or the female’s reproductive tract,” Smith warns.
Chute-side blood tests require a small amount of blood and take 20 minutes or less.
“Some producers like the chute-side tests; some producers find the chute-side tests to be a little harder for them to read on some animals,” Banta says.
Banta’s biggest recommendation for most producers who choose a blood test is to use a 3-cc syringe and 20-gauge needle if they are not comfortable with a vacutainer needle and blood tube holder. He says the syringe will make it much easier to draw blood.
Secondary Methods: Estrous Detection and Calving Observations
Smith says two secondary methods that may be valuable complements to the primary methods are estrous detection and parturition.
“Heat detection is simple and inexpensive, as it requires no equipment or only requires low-cost supplies if using a heat detector or marking paint,” Smith explains. “The major cost is associated with the time and labor required to detect heat.”
Smith adds false negatives can be an issue and heat can be hard to detect in large groups.
“Some pregnant cows will also stand to be ridden, which limits estrous detection’s utility for pregnancy diagnosis,” Smith adds.
Calving is a reliable method for obvious reasons, but Banta says that it is important to realize that even though some of those animals were determined to be pregnant, some females are going to lose that pregnancy between pregnancy diagnosis and calving.
“This method limits your ability to make early, informed management decisions, and more specifically, make decisions on what to do with cows that remain open following a defined breeding season,” Smith says.
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