The test is intended for use as an aid in monitoring progesterone levels in dairy cows, primarily to identify oestrus for optimal AI timing, also identifying earlier if she's not pregnant, if she returns to heat 19-23 post AI. It is designed for self-use, cow-side so no specialist expertise required.

Yes, it would be a oestrus, ‘heat’ confirmation using the dip in P4 (a Low progesterone result, <2 ng/mL reading).

but also:

• Preventing mistimed insemination

• Preventing insemination of an already pregnant cow

• Preventing incorrect calving dates and mistimed dry periods

• Detect silent heats

• Improve PD percentages

• Help you investigate poor fertility

• Help you investigate non-cycling cows

• Help you diagnose problems such as persistent corpus luteum

• Work alongside other heat detection methods to remove false positives

• Detect non-pregnant cows 19-23 days post insemination

Unlike behavioural heat detection, P4 HeatRead™ is a rapid milk test that measures progesterone, a hormone that tells you exactly where a cow is in her reproductive cycle.

Research shows up to 30% of cows do not show behavioural indicators of heat, including standing heat and other bulling behaviour.¹ Even in cows which do exhibit these behaviours, they are not necessarily a true indicator of heat. Progesterone testing is 99% accurate in determining if a cow is in heat.² P4 HeatRead™ allows you to identify if a cow is in heat with a high degree of certainty in only twenty minutes.

P4 HeatRead™ is non-invasive, easy and accurate: 100% sensitivity, 98% specificity v’s ELISA.³ It can be used to improve AI percentages, give insight into poor fertility, help your vet to diagnose fertility problems, and work alongside other heat detection methods to remove false positives.

• Identify if your cow is in oestrus ‘heat’ to ensure the correct timing of Artificial Insemination.

• Detect non-pregnant cows early - When tested 21-24 days after the AI, if the cow has a low progesterone level, she is back in heat, and isn’t pregnant. It is then safe to AI again.

• Detect return to cycling after calving by testing once a week for three weeks from 45 days after calving. You should see at least one low result. The next heat can be calculated by counting 21 days from the low result.

Through heat confirmation, P4 HeatRead™ can save you money on wasted straws, AI technician fees or unnecessary culling. It can help you improve your herd productivity by increasing your reproductive performance. Without progesterone testing, up to 5-26% of cows can be sent to AI when not in oestrus,⁴ meaning wasted costs and longer calving intervals.

Particularly in block-calving, missed heats and long breeding seasons have a major impact on farm profitability.⁵ With accurate and consistent identification of heat, cows can be sent to AI at the correct time. 

Missed heat and poor fertility costs approximately £240 per cow per year, a sector wide loss of £475 million in the UK alone.

If you run the test 19-23 days after service and the test shows high progesterone, she may be pregnant. A low progesterone result identifies non-pregnant (open) cows, so they can be re-bred without delay.⁶ If the test is not done on day 19-23, a high progesterone level may not indicate pregnancy and might be a normal part of her cycle.

The test can be repeated 42 days after AI to ensure the cow remains in calf. The test will show a high progesterone level if she is still pregnant.

A cow with poor condition or nutrition may have a relatively low progesterone level and still be pregnant. In this case, we recommend confirmation by diagnosis e.g. PAG or ultrasound.

No, this serves as early detection of non-pregnancy, so this test allows cows that are confirmed open to be inseminated again. Even if the cow is pregnant at 21 days, many pregnancies are lost in the first 5 weeks, so later checks can be used to confirm that the pregnancy is sustained.

It can be a first step in identifying cows that appear not to be cycling (lack of bulling behaviour) but are actually in silent heat. If a cow appears not to be cycling, test weekly for three weeks. Three of the same results over a three-week period could mean she is cystic or anovular. If this happens, please consult your vet.

The day you test on will be determined by what you are using P4 HeatRead™ for. If you want to check that a cow is genuinely in heat then you can test when she is showing signs of heat, or when you suspect she is in heat according to her cycle or other heat detection devices.

If you want to check whether a cow has returned to heat after AI then you should test between 19-23 days post-AI and then at 42-48 days again if necessary. These days are important as progesterone rises in between heats in a non-pregnant cow but remains high in a pregnant cow, so your result could either indicate she has returned to cycling (Low result) or she is pregnant (Not Low result).

If you wish to detect the timing of heat, then test once weekly for three weeks. You should get one Low or Medium result, indicating heat just before or after this day. You can do further tests daily to determine when your cow goes into heat.

If testing immediately after calving, then begin testing three weeks (21 days) after parturition.

The test can be used on fresh or on fresh milk that has been frozen. It’ been tested across all milk types including breed of cow e.g. Normal cycle, pregnant, post-calving, Holstein, Friesian and Jersey.

The bulling is false.

Oestrogen waves can occur during pregnancy and cause signs of bulling. Checking the progesterone level can reassure you that the cow has high progesterone due to pregnancy or not being in heat and should not be re-inseminated. Insemination of a pregnant cow risks aborting the pregnancy and increases risk of infection.

Testing once a week for three weeks from 45 days after calving will help to determine if the cow has started cycling again. If you get a LOW result, then she is cycling.

The kit inc. strips, buffer are to be stored in a dry environment at temperatures between 2°C and 30°C.

1.Holman A, Thompson J, Routly JE, Cameron J, Jones DN, Grove-White D, et al. Comparison of oestrus detection methods in dairy cattle. Vet Rec. 2011;169(2):47. doi:10.1136/vr.d2344. 

2.McLeod BJ, Foulkes JA, Williams ME, Weller RF. Predicting the time of ovulation in dairy cows using on-farm progesterone kits. Anim Prod. 1991;52(1):1–9. 

3.P4 Science. Internal validation study. Data on file. 2025

4.Hoffmann B, Günzler O, Hamburger R, Schmidt W. Milk progesterone for fertility control in cattle… Br Vet J. 1976;132(5):469–476. 

5.Beukes PC, Burke CR, Levy G, Tiddy RM. Using a whole farm model to determine the impacts of mating management on the profitability of pasture-based dairy farms. Anim Reprod Sci. 2010;121:46–54 

6. Booth JM, Davies J, Holdsworth RJ. Use of the milk progesterone test for pregnancy determination. Br Vet J. 1979;135(5):478–488.