| Care of the Broodmare Following Covering or Insemination |
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Pregnancy diagnosis in the mare There are a number of procedures used to confirm that a mare is in foal Rectal palpation This can be done at any stage from day 14-15 after ovulation (16 – 17 after covering) onwards. The vet assesses the tone, size and position of the uterus which change 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. Ultrasound scanning This is the most commonly used method for pregnancy diagnosis and the assessment of early foetal growth. It is performed from day 14-15 after ovulation (16 – 17 post covering) onwards. It is the most reliable method of detecting unwanted twin pregnancies. To be rule out twins it is sensible to scan the mare at least twice, once as above and the second time approximately 28-30 days post ovulation The procedure To scan a mare during early pregnancy, an internal examination of the mare is required. To ensure this is done safely for both vet and mare, it is important that the mare is properly restrained; stocks are ideal. Electricity is required to power the scanner plus sufficient area out of sunlight to clearly view the scanner screen, To perform the scan the ultrasound probe is introduced by the vet into the mare’s rectum and advanced until it lies over the uterus. It is moved from side to side, passing over the uterine horns and the ovaries. An image is seen on the screen. If the mare is pregnant, the embryonic vesicle appears as a distinct black sphere on the screen. When mares are examined as early as day 14 – 15 after ovulation, they are checked again a few days later. The embryo itself can be seen as a white speck within the circular black area between days 18-21 after ovulation. Even at this early stage, the pulsation of the heart is often visible. By day 26, the embryo is clearly visible as it lifts away from the wall of the vesicle and protrudes into the lumen A third examination is ideally carried out around day 28 and before day 35 to ensure that the mare is still pregnant and to make certain that a twin has not been missed. The optimum time for determining the gender of a foal in utero is between 55-65 days. Blood tests- 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 around 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 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. Urine tests 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 |
