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Analyzying pregnancy diagnosis

published: September 6th 2018
by: Ky Pohler
source: Texas A&M University

Pregnancy diagnosis. Producers need to find a method that works for them.

When do cows experience pregnancy loss?
95% of time fertilization occurs.
By day 28, pregnancy has dropped to 70%, a 25% loss of pregnancies. This is referred to as early embryonic loss.
By day 42, we lose 8% more pregnancies, the pregnancy rate is now around 62%. This is late embryonic loss.

Cows all cost the same to manage. If they don't have a calf or have a calf born late in the calving season, they cost us money.

Knowing pregnancy status of the herd helps make management decisions. They can help with drought management (sell open cows) and marketing decisions. Pregnancy diagnosis also helps us evaluate bull or semen fertility and breeding program success.

Pregnancy diagnosis doesn't cost a lot, but provides a great economic benefit.

What is the ideal pregnancy test?

  • High sensitivity (correctly identify pregnant animals)
  • High specificity (correctly identify open animals)
  • Simple
  • Cost effective

If a cow calves, we know she was pregnant. There are manual diagnosis, ultrasound, and chemical based diagnostics.

Rectal palpation of pregnancy looks at presence of fluid, may be able to identify amnion, fetus, placental junctions, or membrane slip.

Ultrasound pregnancy diagnosis requires a skilled professional. There is nearly 100% accuracy of ultrasound at >27-28 days of gestation. The difference between rectal palpation and ultrasound is feeling versus seeing.

There are currently two types of chemical based pregnancy diagnostics. Pregnacy associated glycoproteins (PAGs) are produced by pregnant or recently postpartum cows. PAG testing works through an ELISA assay. There are a series of washes and incubations that look for the presences of PAGs.

IDEXX, bioPRYN, and Genex sell PAG-based tests. All available tests are accurate and recommended for use.

PAGs are low in the first two months. They start to increase at the third month. Accuracy of PAGs ranges from the low 90s to the high 90s.

How early can we detect PAG and successfully diagnosis pregnancy? The earlier we move pregnancy detect, the more possiblity we have for pregnancy loss after the pregnancy check.

PAGs are first at high enough levels to detect at day 24. About 11% of heifers identified as pregnant at 24 days lose their pregnancy by day 32.

Heifers that successfully maintain a pregnancy have higher levels of PAGs than those that eventually loss the pregnancy.


  • Rectal palpation, ultrasound, andPAG testing are effective methods of pregnancy diagnosis in cattle. 
  • Embryonic mortality between day 17 and 31 of gestation provides a major challenge for early pregnancy diagnosis.
  • No matter what... Use a proven method of pregnancy diagnosis!

From presentation at the Applied Reproductive Strategies in Beef Cattle Conference

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