“The other major reason to pregnancy test is that finding more than a typical number of open cows can alert you to a disease problem,” he says. Trichomoniasis, vibriosis, IBR, BVD, and lepto may cause cows to lose their pregnancies. Typically the sexually transmitted diseases like trich and vibrio cause early abortion and the cow returns to heat, ending up open or calving very late. If bulls are left with cows all summer, some of these cows may become pregnant again. Finding you have a bunch of open or late cows is a little after the fact, but at least you’ll know there’s a problem and can take measures to correct it.

“Nutritional deficiencies in the herd may also show up as open cows, especially in second calvers. Most people feed yearling heifers adequately and they breed up fairly well—but they are not raising a calf,” says Hoffman. The 2 year olds with calves at side are still growing, plus trying to feed their calf. That age group may end up with a high percentage open.

“Some people overfeed and pamper replacement heifers (weanlings and yearlings) to make sure they’ll breed, then after their first calf they don’t get any special treatment and lose weight—and don’t rebreed.” This group has the hardest job; some ranchers give them a second chance if they didn’t breed up as early, especially if they raised big calves.

“Yearling heifers, by contrast, should have a short breeding season (45 days, the equivalent of 2 heat cycles),” he says. This is the age to sort and cull, regarding fertility and efficiency. Pregnancy testing heifers soon after a relatively short breeding season is helpful because you should never keep a yearling that’s a slow breeder (her fertility problem is probably genetic, rather than nutritional). You can then sell the open ones early in the summer when the market for them is best.

If you are trying to determine when cows were bred in order to predict when they will calve, preg-checking is never 100 percent accurate. “There’s enough individual variation among cows to make it difficult. A cow can calve up to 2 weeks ahead of her ‘due date’, or up to two weeks later. An example that illustrates this was a study looking at length of calving season. In this study, 100 heifers were synchronized and bred on one day. Even though they were all bred the same day, their calving season was a month long, with some calves arriving two weeks ahead of their due date and some two weeks late,” explains Hoffman.

“Personally I’ve noticed when ultrasounding cattle, that I’m not as accurate in my palpation (in determining stage of gestation) as I thought. There’s enough variation in cows, when palpating rectally, that you can be fooled. Some are farther along than what they feel like (when assessing the size of the uterus, amount of fluid, etc.) and some are a little shorter,” he says. Taking the bull out after a defined breeding season helps when it comes time to pregnancy test because it eliminates those questionable ones that may have just been bred but can’t be definitively determined by palpation.

Early in pregnancy the veterinarian can usually determine and date pregnancy by the size of the uterus, when palpating. “As the cow gets a little farther along you can actually bump the fetus within the uterus. When she gets to about 100 to 110 days of gestation, the uterus has dropped down farther below the pelvic rim and you can’t reach the entire uterus. At this point you go by the size of the buttons (cotyledons). As a back-up you can assess the diameter of the uterine arteries. When you get past about 4 months, you do a lot of the aging mainly by the size of the cotyledons. There will be some tiny changes, so it is easy to be a couple weeks off in your estimation of the length of pregnancy,” says Hoffman.

Ultrasound is another option. “It’s more accurate, especially for dating when the cow was bred and when she should calve. Ultrasound can be done earlier than palpation and be very accurate. You can diagnose pregnancy earlier, if you wish, and send the open ones to market sooner. With ultrasound, you can actually see the embryo or fetus at 21 days or even a little earlier” he says.

“The cost of ultrasound is about twice that of rectal palpation, but the improved accuracy is worth it, to many producers. Ultrasound is the standard method in most dairies, not only because of better accuracy, but also because you can diagnose ovarian problems and other reproductive issues. In beef cattle, ultrasound isn’t used as much yet, but I have a friend in Montana who is ultrasounding most of the larger beef herds in his region. The ranchers have corrals out on the range and he runs an inverter off his truck to power the ultrasound machine,” explains Hoffman.

“Ultrasound isn’t 100 percent accurate, but it’s more accurate than palpation, especially when checking cows early. By the time a cow is 5 or 6 months along the odds of calling her open when palpating are small, compared to checking her at 30 days,” says Hoffman.
Another advantage of ultrasound is your ability to see the sex of the fetus. This is helpful in purebred operations if they want to sell a group of cows or heifers that will all have bull calves, or all have replacement heifers.

“In our region I’ve only done a few commercial herds. One producer had me ultrasound a bunch of older cows that had only been bred for a short time. He wanted to see if they were pregnant before he culled them (keeping the pregnant ones another year), and at that stage of their pregnancy ultrasound was more accurate than palpation,” says Hoffman.

One down-side to early checking is that it’s possible to have some early abortions; a cow that checked pregnant may end up open or very late instead. If you leave the bull with the cows this may mean some of those cows will breed back to be late calvers.

Blood Test Preg Check
The newest option for pregnancy testing is a blood sample. This technology was developed by Dr. Garth Sasser (University of Idaho). He discovered a protein produced by the placenta of ruminant animals, detectable in their blood. He founded a company called BioTracking and created a blood test called BioPRYN (Pregnant Ruminant Yes/No) for cattle, sheep, goats, and other ruminants. This test became commercially available for cattle in 2002 and there are now 24 labs around the world that handle blood samples.

According to Jeremy Howard, marketing manager, more than 362,000 samples had been processed by the end of 2009 and the number tested annually keeps growing. Advantages of the blood test over palpation include being able to detect pregnancy a little sooner with better accuracy. The blood test is cheaper than ultrasound and more accurate than rectal palpation. It can be done more quickly and easily, taking the sample from a vein under the tail. This is much less invasive, less traumatic, and safer for the animal than palpation, says Howard. There’s no risk for spreading disease from one cow to the next, as can happen when doing rectal palpation (since very few technicians take time to change sleeves and use a new one for each cow).

You can do more animals in a shorter time, taking blood samples. Ranchers can do this themselves. It’s sometimes hard to schedule a vet to come to the ranch for palpation or ultrasound during the busiest preg-checking seasons, and on ranches located a long way from a vet, the cost of a farm call makes palpation more expensive than the blood test. Samples are labeled with the cows’ numbers and shipped to a lab, with results sent back by phone, fax or e-mail.

“For the blood test, all you need is a syringe and needle. Cost per sample is $2.40. We can also do our BVD test from those samples at an additional cost of $3.65, if the rancher wants both tests done at the same time,” says Howard.

A growing number of beef producers are testing their heifers 30 days after pulling the bull or after synchronizing and breeding AI. Any heifers that are open can then be sold at the peak of the open heifer market before they’re too old to get top beef prices and before the market drops in the fall when everyone is selling cull cattle.

The blood test is a great tool if a rancher waits 2 weeks after AI breeding before putting a cleanup bull with cows. With this test you can tell which ones conceived to the AI breeding and which ones were bred later to the cleanup bull. Breeders using embryo transfer can check the recipient cows quickly to determine which ones are pregnant, and have another chance to use the ones that didn’t take.

Feedlot heifers can be checked upon arrival to see if they are pregnant. The test is also useful in sale barns, to market cows more efficiently. For instance, after using the blood tests one auction owner found that 34 to 40 percent of the cows being called open by a veterinarian doing palpation were actually pregnant—especially the ones that had been bred during the 2 months prior to checking them. By knowing they are pregnant, he is able to sell them as bred cows rather than as open culls.