How does PregCheck30 accurately determine if a cow is pregnant?

PregCheck30 measures the amount of a protein called PAG (Pregnancy Associated Glycoprotein) in a cow’s milk.

•  If levels are over 0.30 units, the cow is pregnant.
•  If levels are under 0.15 units, the cow is not pregnant, or is very early in pregnancy (under 30 to 40 days)
•  If the levels are between 0.15 and 0.30 units the result is doubtful and the cow should be rechecked later.

Accurate diagnosis depends on a cow being at least 30 days post-mating, although sometimes cows as early as 28 days will give a positive result. Testing at the right time will ensure nearly all cows are clearly diagnosed as ‘pregnant’ or ‘not pregnant’.

How can I be sure PregCheck35 results are accurate?

PregCheck30 is effective when the following logical but key requirements are met:

To accurately interpret PregCheck30 results, cows should be at least 30 days past their last known mating date, although sometimes cows as early as 28 days will give a positive pregnancy result.

1.  A well planned and run farm management system (based on either seasonal calving or split calving with batch mating) will ensure you easily identify cows ready for testing.
2.  Identifying cows accurately is critical. An accurate test result can only be achieved if individual cows are correctly identified.
3.  You still need good records of known mating dates to calculate predicted calving dates and determine drying off dates. Even your vet looks to mating records to confirm probable calving dates.

Has the accuracy of PregCheck30 been validated by research?

Yes. Prior to its release in 2012, a number of carefully controlled field trials were carried out on over 1,000 dairy cows. These trials clearly establish the accuracy of the PregCheck30 milk pregnancy test.
Since the product was released, commercial results on thousands of milk pregnancy test results have been compared with conventional pregnancy diagnosis (ultrasound or rectal palpation).
The results confirm that in normal commercial dairying situations, PregCheck30 is over 98% accurate at diagnosing pregnant and empty cows from a single milk sample when cows are over 30 days pregnant as long as cows and milk samples are accurately identified.

Can the test be used to detect pregnancy in other species?

Yes. The test has recently been validated by IDEXX to provide a laboratory based method for the detection of pregnancy in goats using a milk sample. The test is suitable for use on goats which are at least 28 days post-mating.

Will the test results be affected if cows are being treated with, for example, antibiotics?

No. The protein measured to determine the pregnancy status of your cows is not affected by other drugs or treatments.

How soon after calving do protein levels return to normal levels?

PAG levels decline rapidly after calving, by 60 days post calving the protein levels are below the cut off (0.15 units) in 100% of cows.

If the test can be done at 28 days, why does TasHerd recommend 30 days?

We suggest waiting to milk pregnancy test your cows with PregCheck30 until 30 days after joining or later. The test can be done at around 28 days and is quite accurate at that time - some Herd Improvement Centres recommend this. The reason we suggest waiting until at least 30 days is because of early fetal loss. Up to 3% (or even more) of cows will “slip” (abort) between 25 and 50 days of pregnancy. This is a natural occurrence and is probably due to “defects” in the developing fetus, which may or may not be due to genetic causes such as mutations.

So, if the test is say 98% accurate for pregnant cows and there is a further 2 or 3% loss after the milk pregnancy test is done, the final accuracy at calving for PREGNANT cows will be down to around 95% or less if the test is done around 28 days, which we believe is too low. However, the test will still be 97% accurate or above for EMPTY cows if it is done at around 28 days.

Can I estimate conception dates from the PAG levels?

No, this is not possible. Once levels are above the cut-off levels allowing for a positive pregnancy test, PAG levels among cows will vary widely as shown in the graph.
The points above and below the red line show the range of PAG values for different cows at the same stage of pregnancy. Even though the values vary widely between cows, the values are all above the cut-off level for pregnancy (the blue horizontal line) from early in pregnancy.