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Pregnancy testing.
There are various methods available for the determination of pregnancy in mares. We will advise you on the best method for your mare, which may vary with each circumstance.
1. Manual rectal examination.
A veterinary surgeon puts a hand in the rectum and feels the uterus for signs of pregnancy. These include uterine tone, the shape of the uterus, and the presence and size of the small sac containing the foetus, called the amnionic vesicle.
2. Ultrasound.
A veterinary surgeon places a probe in the rectum of the mare and sound waves are used to generate a picture of the uterus, the foetus and placenta. It can also detect the foetal heartbeat.
3. Equine Pregnant Mare Serum Gonadotrophin (PMSG) – Laboratory Test.
A blood sample can be taken to test for PMSG which is produced from the lining of the uterus (in structures called endometrial cups) from about day 40 - 120 post mating and it is the best early pregnancy test. PMSG is prone to false positives as, if the foal dies, the lining of the uterus may continue to produce PMSG for some time. A positive PMSG test should be followed by an Oestrone-Sulphate test (see below), which will confirm pregnancy and the presence of a live foal after 100 days.
4. Equine Oestrone Sulphate Pregnancy Test – Laboratory Test.
A blood sample can be taken to measure Oestrone Sulphate, which starts to rise from about 80 days post mating, increases steadily to above 25 ng/mL and remains detectable until very close to foaling. Oestrone Sulphate can be used as a very sensitive pregnancy test in horses and demonstrates the presence of a live foal, if the foal dies the Oestrone Sulphate decreases very rapidly.
5. Total Urinary Oestrogens – Laboratory test.
Total Urinary Oestrogens may be used as a late pregnancy test (>100 days gestation) as there are very large concentrations of a variety of oestrogens excreted in the urine in late pregnancy. A urine sample must be collected and submitted to us – approx 250ml.
Summary table of laboratory tests for equine pregnancy.
Days of Gestation Test Use
45 - 100 PMSG Good indication
>100 Oestrone Sulphate Middle/Late - very accurate
>100 Total Urinary Oestrogens Middle/Late - urine test
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