There are four main ways to pregnancy test a cow: rectal palpation, ultrasound, blood testing, and milk testing. The method you choose depends on how early you need results, the size of your herd, available equipment, and whether you have access to a veterinarian. Most operations rely on rectal palpation or ultrasound performed by a vet, but blood and milk tests have become practical alternatives that don’t require specialized hands-on skill.
Rectal Palpation
Rectal palpation is the oldest and most widely used method. A veterinarian inserts a gloved, lubricated arm into the cow’s rectum and feels the uterus through the rectal wall for physical signs of pregnancy. It requires no equipment beyond a shoulder-length glove and lubricant, which is why it remains popular on operations of every size.
What the examiner feels changes as the pregnancy progresses. At around 30 days, the fetal membranes can be gently “slipped” between the fingers in heifers. By 60 days, the amniotic sac has softened enough to feel a small, mouse-sized fetus directly. At roughly 90 days, the button-like structures where the placenta attaches to the uterine wall (called placentomes) become large enough to feel, and the fetus is about the size of a rat. Most vets won’t attempt palpation before 35 to 45 days because the signs are too subtle and handling the uterus too early carries a small risk of disrupting the pregnancy.
An experienced vet can palpate a large number of cows quickly, often checking one every 30 to 60 seconds once the herd is moving through the chute. Accuracy is high in skilled hands, though it depends heavily on the examiner’s experience, and it’s less precise for determining exactly how far along a cow is compared to ultrasound.
Ultrasound
Transrectal ultrasound works like the ultrasounds used in human medicine, but the probe is inserted rectally and aimed at the uterus. It can detect pregnancy as early as 26 to 30 days after breeding. Color Doppler ultrasound, which measures blood flow to reproductive structures, can pick up signs of pregnancy as early as 20 days, though this level of equipment isn’t common in routine field work.
Ultrasound’s biggest advantage over palpation is the amount of information it provides. Beyond a simple pregnant-or-open answer, it lets you visualize the embryo, confirm a heartbeat, detect twins, and estimate gestational age by measuring the width of the fetal skull or the crown-to-rump length. A skull width of 17 millimeters corresponds to roughly 56 days of gestation, while a crown-rump length of 17 millimeters corresponds to about 34 days. Fetal sex can also be determined during a specific window, typically between 55 and 70 days, by locating the genital tubercle.
Cost for ultrasound and palpation tends to be similar since both depend on the veterinarian’s hourly rate and how many cows are checked per hour. With large groups, per-head costs drop and can be comparable to blood testing. With small herds, expect to pay upward of $4 per cow due to the vet’s trip charge.
Blood Tests
Blood-based pregnancy tests detect pregnancy-associated glycoproteins (PAGs), proteins produced by the placenta that circulate in the cow’s bloodstream. You draw a blood sample from the tail vein, send it to a lab or use an on-farm lateral flow kit, and get a pregnant or open result. Most PAG tests are reliable starting at 28 to 30 days after breeding.
These tests are a good fit for operations that don’t have easy access to a reproductive vet or that want to avoid handling cows through a chute for rectal exams. Processed blood tests generally cost $2.40 to $3.75 per cow, and on-farm kits are now available that give same-day results without sending samples to a laboratory.
One important limitation: PAGs from a previous pregnancy can linger in the bloodstream. If a cow calved fewer than 42 days before the test, residual PAGs can trigger a false positive. This matters most in dairy herds where cows are rebred soon after calving. In studies comparing PAG blood tests to ultrasound, sensitivity (correctly identifying pregnant animals) was 96 to 97%, while specificity (correctly identifying open animals) ranged from 64 to 90% depending on the test brand and protocol. The main source of error is false positives, not missed pregnancies.
Milk Tests
For dairy operations, milk-based pregnancy testing offers a way to check cows without pulling them out of their normal routine. A 10-milliliter milk sample is collected after the fore-strip step during regular milking, then shipped overnight to a laboratory for analysis. The lab tests for the same PAG proteins detected in blood tests.
The appeal is convenience. Cows don’t need to be restrained in headlocks, there’s no need for a vet visit, and the sample collection fits into the existing milking workflow. The trade-off is turnaround time, since samples need to reach the lab and results come back a day or two later. Like blood PAG tests, milk tests share the same 42-day postpartum limitation for avoiding false positives.
Progesterone Testing
Progesterone is the hormone that maintains pregnancy, and its levels in blood or milk can give an early indication of whether a cow has conceived. At 21 days after breeding, if progesterone is above roughly 1.5 to 2.0 nanograms per milliliter, the cow has not returned to heat and is likely pregnant. If progesterone is low, she is almost certainly not pregnant.
The problem is that high progesterone doesn’t guarantee pregnancy. It only confirms the cow still has an active corpus luteum. In one study, about 22% of non-pregnant cows were incorrectly classified as pregnant at the 1.5 ng/mL threshold because they had longer-than-average cycles or had experienced early embryonic death while still maintaining progesterone levels. Progesterone testing is better at ruling pregnancy out than confirming it, so it’s rarely used as a standalone method.
Why Re-Testing Matters
Pregnancy loss in cattle is more common than many producers realize, and it’s the reason a single early test isn’t always enough. By the end of the first month after breeding, nearly 48% of inseminations have failed to produce a viable pregnancy. Most of those losses happen in the first few days and would never be detected by any test. But losses continue to occur: between days 32 and 100, an additional 3 to 6% of confirmed pregnancies are lost, with some herds experiencing rates as high as 42%.
This is why many operations test once at 30 to 35 days, then reconfirm at 60 to 90 days. An early positive gives you useful information for breeding management, but a second check catches the pregnancies that failed after the first test. If you’re selling bred cows or making culling decisions, that recheck protects you from keeping or selling animals that are no longer pregnant.
Who Can Legally Perform These Tests
In most U.S. states and Canadian provinces, pregnancy testing by rectal palpation or ultrasound is legally considered an act of veterinary medicine. Only licensed veterinarians can charge for these services. Ranchers, feedyard managers, and their full-time employees are generally allowed to ultrasound their own cattle under a veterinarian’s supervision or guidance, but the specifics vary by state. A few states have deregulated beef cattle pregnancy testing entirely. Blood and milk sample collection doesn’t carry the same restrictions since you’re simply pulling a sample and sending it to a lab, but it’s worth checking your state’s rules before offering testing services to others.