Pregnancy diagnosis in the mare
There are a number of procedures used to confirm that a mare is in foal. It is best to talk to your vet to decide which would be the most accurate and safe for your mare.
This is the most commonly used method for pregnancy diagnosis and the assessment of early foetal growth. The first scan is performed on day 14 -15 after ovulation (16 – 17 post covering).
It is the most reliable method of detecting twin pregnancies. Two scans are required between 14 – 18 days following ovulation if the mare has double ovulated. The most successful time to remove a twin is during this time. Twins identified after this stage are unlikely to survive.
A heart beat scan is then recommended at 28 – 30 days following ovulation. We can also check there is no twin that has developed during this time.
A final scan is then recommended between 45 – 60 days. At 60 days it may be possible to perform foetal sexing if you wish to know the gender of the foal.
If ultrasound is unavailable or the mare is mid-pregnancy, a rectal palpation can be performed. The vet assesses the tone, size and position of the uterus which changes as the pregnancy advances. The foal may be felt from around mid-pregnancy. The vet may inspect the cervix which is usually whiter and much more tightly closed that the cervix of a non-pregnant mare. The rectal findings during early pregnancy are not always conclusive and cannot eliminate the possibility of twin conceptuses.
Equine chorionic gonadotrophin (eCG):
From days 45-90, a blood sample may be taken and tested for the presence of eCG. This is produced by structures called endometrial cups which form when foetal cells invade the endometrium. The test is approximately 90% accurate. Occasionally a mare produces a false negative result, but inaccuracies more commonly involve false positives. This is because eCG continues to be produced if the foetus dies.
Oestrone sulphate is produced by the foetus and can be detected in the serum of pregnant mares from day 120. The levels fall in the last few weeks of pregnancy.
Oestrogens produced by the placenta and the foetus are present in the mare’s urine from 150 days to full term, but the current testing kits available are not always deemed reliable.