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If PAGs levels are above the blue dotted line, the cow is pregnant.
If PAGs levels are below the solid blue line, the cow is not pregnant, or is very early in pregnancy (less than 28 days’ post-mating).
On rare occasions the PAGs levels are between the 2 lines (known as a re-check), these results are ambiguous, and the cow should be retested later to confirm her status.
After calving PAGs levels rapidly decline. By 60 days after calving PAG levels have returned to baseline and there will be no interference when testing for the next pregnancy. The diagram below shows the decline of PAG levels after calving.


Early embryonic loss

After early embryonic loss or abortion PAGs will continue to circulate. Further research into this is currently being conducted. In early embryonic loss we estimate PAGs will disappear within 7 days. In cases of abortion PAGs may be present for a longer period of time. Foetal loss late in gestation may require up to 60 days for PAG levels to drop below the test threshold.


The Alertys tests are enzyme-linked immunosorbent assay (ELISA) tests run in the laboratory. ELISA is a commonly used scientific test for the detection of peptides, proteins, antibodies or hormones (in this case Pregnancy Associated Glycoproteins). ELISA is one of the most sensitive and reproducible diagnostic technologies available. In general ELISA tests are fast, simple, economical to perform and easily automated.

How do the Alertys Pregnancy Tests work?

The Alertys Pregnancy tests detects Pregnancy Associated Glycoproteins (PAGs). PAGs are an excellent pregnancy marker because they are only produced by the placenta when the cow is in calf. Expression of PAGs starts on the first day of gestation and continues until calving. By day 28 of gestation the expression of PAGs reaches the level required to be reliably detected by the Alertys Milk or Blood based tests.

As an example the diagram below shows the expression of PAGs over the course of gestation through milk.