Species: Equine

Specimen: Serum

Container: Plain tube (red top)

Collection protocol: Standard venepuncture

Special handling/shipping requirements: Standard

General information about the disease: N/A

General information about when this test is indicated:

Pregnancy diagnosis: This is the most reliable means of pregnancy diagnosis in the mare from approximately 100 to 310 days. Increased concentrations of oestrone sulphate indicate a viable foetus and concentrations will drop immediately if foetal death occurs. Oestrone sulphate concentrations can decrease in late pregnancy and can give a negative result in mares in late pregnancy. A non-pregnant mare has an oestrone sulphate concentration of <5 ng/mL. The concentration in a pregnant mare is typically >20 ng/mL and generally around 100 ng/mL.

Cryptorchid (rig) identification: The equine testis produces ten times the quantity of oestrogen compared with testosterone and it is therefore much easier to differentiate a cryptorchid from a gelding by measuring serum oestrone sulphate rather than testosterone. This test is not recommended in horses less than 3 years of age and donkeys, which will require testosterone assay after stimulation with hCG. Note that cryptorchids may not produce sufficient oestrone sulphate concentrations and therefore a low result may not “rule-out” the possibility of retained testicular tissue.

Comparison with other related tests:  

For pregnancy diagnosis, progesterone can be used from days 19-22, and PMSG may be used from days 40-100.  Anti-muellerian hormone can also be used for cryptorchid diagnosis.