Page 940 - The Veterinary Care of the Horse

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Figure 19.18 A 30 day embryo

BLOOD TESTS

Equine chorionic gonadotrophin (eCG)

From days 45 to 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 after formation of the endometrial cups.

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