Is she pregnant or isn’t she?

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You’ve fine-tuned your dairy’s breeding protocol into a well-oiled machine.

Cows are identified and sorted accurately. You’ve trained and retrained employees on proper procedures so that compliance is as perfect as you can make it. Precise records track breeding actions and health programs are in place to ensure that cows are in prime shape.

But what’s missing in this sequence? Answer: timely, accurate pregnancy diagnosis. Without this critical component, a breeding program languishes in mediocrity.

Fortunately, there have been a number of advancements in pregnancy diagnosis in recent years, with more on the way. This is good news as you look to improve reproductive performance.

Here’s an update on the tools you can use to diagnose pregnancies on your dairy.

Q: What’s the latest on progesterone tests?

A: Measuring progesterone in blood or milk as a method to identify open cows was perhaps the first true example of chemical pregnancy-testing, explains Matt Lucy, animal science professor at the University of Missouri. “These tests are excellent at identifying non-pregnant cows, because if a cow tests low for progesterone, then she is not pregnant,” he says. “On the other hand, if she tests high for progesterone, she may or she may not be pregnant.”

A number of commercially available tests are on the market that can be used on-farm or through your veterinarian.

In-line milk progesterone tests from dairy equipment manufacturers are also coming to the market, with more in development. Europe has been a testing ground for these tools. These daily progesterone tests create a more accurate pregnancy diagnosis than single tests because the additional data offer information over a longer time frame. “False-positive cows would only arise from relatively rare cases with a persistent corpus luteum in the absence of pregnancy,” says Lucy.

Q: How do blood protein tests work?

A: These tests can give you an extremely accurate “yes” or “no” answer regarding cow pregnancy status. They are based on the presence of pregnancy-specific protein B (PSPB),which was originally described as being composed of many protein variants. A portion of of these variants are now named PAGs, or pregnancy-associated glycoproteins (PAG). These proteins are secreted by the placenta and can be easily detected in blood.

“Laboratory-based pregnancy testing is one technology that has improved reproductive efficiency on dairies of all sizes within my practice,” says Glenn Pearson, veterinarian in Frederic, Wis.

The original research in this area focused on PSPB which became the basis for the commercially available test BioPRYN from BioTracking LLC.

This enzyme-linked immunosorbent assay (ELISA) can be run as soon as 30 days post-insemination, and cows must be at least 90 days in milk to make sure proteins from the previous pregnancy do no interfere with results. Tests on virgin heifers can also be run 30 days post-insemination, but you don’t have to worry about the 90-day consideration since these animals have not had a previous pregnancy. 

The test is more than 99 percent accurate when it calls a cow open.   It is 93 to 95 percent accurate when it calls a cow pregnant, with some of the lesser percentage being due to embryonic death at time of or after testing and then a follow- up test finds them open. 

The results also allow you to manage open cows. The value of that is you can identify these animals quickly and return them to your breeding protocol.

According to results from the 2007 USDA National Animal Health Monitoring System (the latest data available),  about 4 percent of U.S. dairies use blood pregnancy tests to diagnose pregnancy. But that number has soared higher since the survey was conducted. BioTracking’s figures indicate that the number of assays it and its cooperating laboratories processed jumped from less than 100,000 in 2005 to 567,470 in 2009.

The technology holds significant potential, and especially so in areas facing large-animal veterinarian shortages, predicts Lucy.

Meanwhile, some advances are in store for this technology.

There are about 20 PAGs produced by the placenta that researchers are beginning to explore, says Lucy.  Research on one such PAG was reported in the August 2009 Journal of Dairy Science. The paper details a rapid ELISA PAG test that can be run on-farm in 90 minutes using a temperature-controlled water bath. This test was shown to be accurate from 25 to 29 days post-insemination and can be run as early as 60 days post-calving without interference from the previous pregnancy.

Q: How has ultrasound use evolved?

A: Transrectal palpation of the uterus remains the most common pregnancy diagnosis method. Again, using data from the 2007 NAHMS study, just over 85 percent of dairies relied on rectal palpation to diagnose pregnancies. However, the study also shows that transrectal ultrasound was used on about 27 percent of farms — and the practice continues to climb.

That’s because the information-gathering capabilities of ultrasound far exceeds that of rectal palpation, notes Paul Fricke, University of Wisconsin dairy reproduction specialist.

The information from an ultrasound exam is provided in real-time and cow-side, says veterinarian Kory Bigalk, of Zumbrota Veterinary Clinic in Zumbrota, Minn.

In a paper he co-authored with veterinarian Andy Borrowman, VetLogic, Inc., Nampa, Idaho, that was presented at the Dairy Cattle Reproduction Council’s regional meetings last fall, Bigalk notes that the use of ultrasound allows for a very quick and accurate diagnosis of ovarian function, including detecting the presence or absence of a corpus luteum, differential diagnosis of luteal and follicular cysts and diagnosis of anovular cows.

Ultrasound is also key in diagnosing twins from 28 to 90 days post-insemination, which enables dairies to use special management considerations and identify high-risk calving candidates. The use of high-quality, high-resolution equipment enables users to accurately determine fetal sex after 60 days post-conception, as well.

Bigalk and Borrowman also report that using ultrasound has increased their speed of pregnancy detection by 20 percent.

This technology also enables users to detect pregnancies earlier than with traditional rectal palpation. There is some debate as to how soon it is necessary to try to determine pregnancy status given the amount of pregnancy loss that occurs as between day 26 and day 33. “Based on current resynchronization strategies, the need for a non-pregnancy diagnosis before 32 to 39 days after timed A.I. is questionable,” says Fricke.

Expect this discussion to continue as pregnancy detection technology and breeding protocols evolve.


Check and recheck

The ability to detect pregnancies at very early stages means you need to rethink when you mark cows down as “for sure” pregnant. “If you’re able to detect pregnancies at day 25 or so, you’re diagnosing when 5 to 10 percent of cows will have embryonic loss. Therefore, you need to look at pregnancies a little differently than you have in the past,” says Matt Lucy, animal science professor at the University of Missouri. Cows will need to be rechecked 60 days post-insemination before you consider the pregnancy a done deal.


The perfect preg check

Given the opportunity to design the perfect non-pregnancy diagnosis tool for successful integration into a bovine reproductive management system, Paul Fricke, University of Wisconsin dairy reproduction specialist, says this tool would be:

  • Sensitive. It would correctly identify pregnant animals.
  • Specific. It would correctly identify non-pregnant animals.
  • Inexpensive.
  • Simple to use under on-farm conditions.
  • Able to give instant results.

Even better, the test would able to determine pregnancy status without the need to physically handle the animals. Most currently available methods exhibit one or more of these attributes, but none exhibit all of them, he says.



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