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Progesterone

Ruminants and Horses

Progesterone may aid in confirming pregnancy if it is high at a time it should be low if the animal was not pregnant. This situation occurs when:

  • Samples are collected at a time of expected oestrus if the animal is not pregnant (e.g. day 19-22 or 40-44 post mating in cattle and horses).
  • Samples are collected outside the breeding season. High concentrations at this time indicates there is a functional corpus luteum and as non pregnant animals should be in seasonal anoestrus, the animal would most likely be pregnant. This is useful for seasonal breeders like sheep, deer, alpacas and llamas.

In most species, the serum progesterone concentration during pregnancy is not significantly different from the concentration during the mid-luteal stage of the oestrus cycle. Therefore, a single random high value is not confirmatory of pregnancy if the stage of the oestrus cycle is not known and the sample is taken during the breeding season. However, if the concentration is still high 10 days later, then the animal is most likely pregnant.

A single low serum progesterone concentration (<0.5 ng/ml) indicates the animal is not pregnant.

As well as pregnancy, other causes of persistent corpus lutea will produce high progesterone concentrations and must be considered, e.g. pyometra.

Species:

All

Specimen:

Serum (minimum 1 ml)

Container:

Plain (red top) tube. Do not use gel serum separator tubes.

Collection protocol:

Standard venepuncture

Special handling/shipping requirements:

Samples should be transported to the laboratory within 12-24 hrs. Ruminant progesterone is unstable in clotted blood. Concentrations fall significantly within two hours at 17°C. In ruminants avoid the use of gel tubes and separate serum within two hours of collection.