top of page
  • Writer's pictureIDEXX Livestock EMEA

Importance of early pregnancy testing

Consequences of having open cows on your farm

Getting cows back in calf in a timely manner is a fundamental part of a good dairy farm management. The economic value of pregnancy testing is to find open cows as soon as possible after breeding¹. In other words, pregnancy diagnosis is about finding the open cows rather than the pregnant ones.

Cows with extra days open can result in large economic penalties to a farm:

Profit increased by reducing open days

Overall, for an all-year calving herd, it costs in the region €5 per additional day to get a cow back in calf, compared to the optimal time. For block-calving seasonal herds, not becoming pregnant within the block has an even greater cost. Imagine if a cow remains open for 20 days longer than expected, farmers can lose up to €100 for a single cow².

Average profit improvement for a farm with 100 cows:

  • 10 days: €5,000

  • 20 days: €10,000

Where do pregnancy losses occur?

It is worth looking in a little detail at early pregnancy in cows, and where the losses occur. Typically, for high yielding dairy cows, we think of pregnancy rates being in the region of 45%. This means of every 100 cows which are served, only 45 of them are diagnosed as pregnant.

Immediately, we introduce some factors around this definition. For example, the proportion which are diagnosed as pregnant will vary depending on how early that diagnosis is made. A 45% pregnancy rate would be typical in a high yielding Holstein herd when the pregnancy diagnosis is made at around 35-40 days after breeding. So if 100 cows are served, why do only 45 of them end up being pregnant five weeks later? Let’s take a look at what typically happens (see Figure below).

Of 100 services, around 90 actually result in a fertilised egg (assuming the service was on time, using fertile semen, and the insemination technique was reasonable)³.

Of these 90 fertilised eggs, only around 2/3 of them will successfully grow and develop into a pregnancy which securely implants into the mother’s uterine lining. Failure of implantation is where the biggest proportion of losses occurs, and it is thought to be because of failure of maternal recognition of pregnancy⁴. Implantation is complete by around day 16-17.

The failure of fertilisation and failure of implantation before day 16/17 should both result in the cow returning to heat at her usual interval, around three weeks after the previous oestrus. Losses beyond this time point result in the cow having an irregular interval between heats.

Once implantation has occurred, the pregnancy is much more secure. Some embryo losses at this stage is inevitable, however, and by about 35 days after breeding, in a high yielding Holstein herd, there will be around 45 pregnancies from the original 100 services: a 45% pregnancy rate⁵.

By 4 to 5 weeks after service, the pregnancy is quite assured. Even so, it has been estimated that around 15% of pregnancies will be lost after approximately day 30⁵. The vast majority of these (12-13%) will be lost from day 30 until day 77, with a further 2-3% lost as more visually obvious abortions after this point. All of these figures are approximate, and there is much variation between herds, depending on factors such as disease control, uterine health and genetics.

When to check for pregnancy

Whatever the method of pregnancy diagnosis, it is useful to do a confirmatory test after around 70-110 days post breeding⁶. The earlier the initial pregnancy test, the more important the confirmatory test is.

The value of doing an initial pregnancy test early is to quickly identify the open cows so they can be re-bred. Most open cows should have been detected in oestrus at the 3-week return point. However, some balance needs to be struck. If we test too soon, a greater proportion of pregnancies will be lost (a confirmatory test is definitely required) and if we test too late, we aren’t getting the advantage of finding those open cows to serve again.

In summary, early pregnancy testing helps to get cows back in calf within a timely manner and PAG testing from IDEXX is a reliable and convenient way of doing so.

The Alertys (PAG) tests are based in the same technology: detection of pregnancy-associated glycoproteins (PAGs). Unlike progesterone testing, PAGs are only produced in the presence of an embryo or foetus, making the tests more reliable.

The tests can be validated from 28 days post AI and throughout gestation, with accuracy of 99% on par with ultrasound or palpation.

We have laboratory-based, in-clinic and on-farm testing options, which will be available for blood or milk samples. Visit our website to learn more >


1.Fricke, P. M. 2002. Scanning the future—Ultrasonography as a reproductive management tool for dairy cattle. J. Dairy Sci. 85:1918– 1926.

2.De Vries, A. Determinants of the cost of days open in dairy cattle. Proceedings of the 11th International Symposium on Veterinary Epidemiology and Economics, 2006.

3.Wiltbank, M. C., G. M. Baez, A. Garcia-Guerra, M. Z. Toledo, P. L. Monteiro, L. F. Melo, J. C. Ochoa, J. E. Santos, and R. Sartori. 2016. Pivotal periods for pregnancy loss during the first trimester of gestation in lactating dairy cows. Theriogenology 86:239–253.

4. Pohler, K. G., J. A. Green, T. W. Geary, R. F. Peres, M. H. Pereira, J. L. Vasconcelos, and M. F. Smith. 2015. Predicting embryo presence and viability. Adv. Anat. Embryol. Cell Biol. 216:253–270.

5. Ealy, A., Z. K. Seekford. 2019. Symposium review: Predicting pregnancy loss in dairy cattle. J. Dairy Sci. 102:11798-11804.

6. LeBlanc, S. J. 2013. Short communication: Field evaluation of a pregnancy confirmation test using milk samples in dairy cows. J. Dairy Sci. 96:2345-2348.



bottom of page