Question 1

What is PAG and how do the Alertys tests detect it?

Accepted Answer

​PAG is shorthand for Pregnancy-Associated Glycoprotein.
The PAG test which has been developed by IDEXX is called the Alertys Pregnancy Tests*. It is an enzyme-linked immunosorbent assay (ELISA) test. It has been developed to accurately detect PAG molecules in blood, serum or milk. It is validated to be used for pregnancy diagnosis in cattle, sheep, goats, water buffalo and bison. Unlike other chemical tests for pregnancy using progesterone as an indicator, the PAG test is very specific for pregnancy.

*The Alertys Rapid Visual and OnFarm pregnancy tests can be run without ELISA instrumentation.

PAGs are detectable as early as 28 days after insemination, so it is recommended that the test can be used from this point and throughout the whole gestation period.

https://www.youtube.com/watch?v=GUp0yxNzUUg

Question 2

What lab equipment do I need to perform the Alertys Milk and Ruminant Pregnancy Test?

Accepted Answer

For performing these tests, you should have a lab equipped for ELISA testing, including pipettes, pipette tips, distilled water, a 96-well plate reader, a microplate washer, and a plate shaker/incubator. All details can be found in the kit inserts.

Question 3

What is the difference between PAG and Progesterone?

Accepted Answer

Progesterone is a hormone that occurs with peaks and valleys during the normal reproductive cycle and is not pregnancy specific.

The Alertys pregnancy tests detect pregnancy-specific proteins called pregnancy-associated glycoproteins (PAGs). These specific proteins are expressed in the embryonic regions of the placenta and detected in maternal fluids such as blood and milk.

Question 4

What are the differences among IDEXX Alertys products?

Accepted Answer

The Alertys Milk Pregnancy Test uses milk samples collected during routine milk recording or collected from self-sampling pots, which will be most suitable for dairy farms. The test cannot be performed on-farm as specialist laboratory equipment is required.
 
The Alerty Ruminant Pregnancy Test, which uses blood samples, on the other side, may be more convenient for beef herds. Again, the samples are tested in a lab as specialist equipment is required.

For smaller-scale testing organisations, such as individual veterinary practices, the Alerty Rapid Visual Pregnancy Test can be used. A blood or serum sample is required, and the test can be completed in around 30 minutes. Some technical skill is required, and this isn’t a cow-side test, but there is no necessity for specialised laboratory equipment to observe the colour change to make a pregnancy diagnosis.

Finally, there is an Alertys OnFarm Pregnancy Test, which was recently introduced in 2021. This lateral-flow style test can be used on farm and requires no technical expertise, other than to collect a blood sample (EDTA sample). A measured amount of blood is dropped onto the test cartridge, and a pregnancy diagnosis result is ready in a matter of minutes, not unlike a human home-pregnancy test kit. This is suitable as a cow-side test.

Question 5

What is the return on investment from using Alertys tests?

Accepted Answer

Open cows can have a major impact on profitability.

Research shows that the average cost per open dairy cow is €5 a day*. These costs include the value of the milk the cow would have produced, the value of her calf, and other relevant factors. Dairy farms can optimise profitability by shortening the calving interval and reducing the number of days that cows are open.

For beef farmers, shorten calving intervals with safe, ongoing confirmation of pregnancy status at critical stages, saves an estimated $77 per head** by identifying and removing sub-fertile cows early.

* De Vries et al, Economics of improved reproductive performance in dairy cattle (Publication AN 156), Gainesville FL, University of Florida Institute of Food and Agriculture Science; 2005 
** Cook B, Biermacker JT, Childs D. The value of pregnancy testing beef cows. Paper presented at: 2007 Southern Agricultural Economics Association Annual Meeting; February 4–7, 2007; Mobile, Alabama.

Question 6

Can all the Alertys tests tell anything else besides pregnancy?

Accepted Answer

No, the test will provide a pregnant, open/non-pregnant or 're-check' result. It cannot tell the stage of gestation, the sex of the calf or if the cow is carrying multiple calves.

Question 7

Why test more than once during gestation?

Accepted Answer

During the normal gestation process of a cow, approximately 10-25% of pregnancies will be lost between conception and full-term due to unknown causes. Pregnancy testing at specific times throughout gestation helps improve reproductive efficiency by finding cows who have experienced pregnancy loss.

It is recommended to test 2-3 times throughout gestation; first at 28-30 days post- breeding, again at 60 days post-breeding, and before dry off to be sure only pregnant cows are kept on farm.

Question 8

Does PAG testing replace the need for a Vet?

Accepted Answer

It is clear there is a strong case for early and accurate pregnancy diagnosis in dairy herds. The method used for pregnancy diagnosis is somewhat a matter of personal choice, depending on individual circumstances and convenience.

Both transrectal ultrasound (TRUS) and PAG testing are reliable methods of early pregnancy diagnosis. Most dairy farms find that working closely with a progressive veterinary practice carries many benefits. This remains the case whether you choose to use the Vet for TRUS pregnancy diagnosis, or not. Of course, transrectal ultrasound can play a role in other areas of fertility management too, such as diagnosis of non-cycling or cystic cows. A mix-and-match approach can be a sensible way forwards for many herds, taking advantage of PAG pregnancy diagnosis for its timeliness, simplicity, and accuracy, whilst reducing the numbers of cows needing to be separated and presented at the routine vet visits. Some farms find this then frees up their Vet to focus on valuable tasks, such as fertility data analysis, training, and other beneficial work.

Question 9

Is there an influence of breed on all the tests?

Accepted Answer

No breed influence on test performance has been described.

Question 10

Do antibiotics influence the PAG tests?

Accepted Answer

IDEXX has no evidence to date to suggest that antibiotic treated milk has a negative effect on the test results.

Question 11

After early embryonic losses or abortion, does the test still detect PAGs?

Accepted Answer

Yes, PAGs will circulate in milk and blood for a certain period of time after embryonic loss or abortion. For early embryonic loss, we estimate PAGs will disappear within 6-10 days. In case of late term abortion PAGs may be present for a longer period of time (40-60 days). It should be noted that it can take up to 60 days for PAGs to drop below the test threshold post-calving.

Question 12

I have a bull in my herd or use a bull at the end of my AI period. Can I still use PAG testing methods?

Accepted Answer

You can still use one of the Alertys tests, you just need to apply some rules around testing. For example, test 50 days after the cow is put with bull (21 days for heat plus 28 days to earliest test), or test 28 days after the bull is removed from the herd.

If the bull is running with the herd all the time, you may need to test monthly, BUT remember, the test will not tell you how far in calf the cow is. And a negative result does not mean not-pregnant if test is done less than 28 days since service.

Frequently Asked Questions

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PAG Testing

Alertys Milk Pregnancy Test

Alertys Ruminant Pregnancy Test

Alertys OnFarm Pregnancy Test

Alertys Rapid Visual Pregnancy Test