... milk progesterone

Progesterone is a hormone produced by the cow during ovulation and can be detected from samples of milk. Progesterone rises and falls during different periods of the cows reproductive cycle. A typical cycle is around 21 days in duration. For the majority of the cycle progesterone is at higher levels and will drop a few days before the cow comes in to oestrus and starts bulling. The progesterone level is at it’s lowest when the cow is actually bulling and remains low for around 4 to 6 days after when it will start rising. The progesterone will rise to a peak before falling sharply a couple of days before the next oestrus.

Since progesterone follows a certain pattern it is possible to take samples from a cow and predict when the next oestrus is likely and thus when it is best to inseminate. This is the first use of progesterone. Any problems with the cows fertility should show up in the progesterone samples and taking a reasonable number of samples can confirm an abnormal progesterone pattern – this can then be used to help determine the right fertility treatment. Once samples are taken and the progesterone levels found these can be used as an aid to the vet and farmer on the fertility situation.

A further use of progesterone is to monitor levels in response to insemination to determine the pregnancy status. A low level on the day of insemination gives a good indication that the cow was in oestrus and subsequent levels should rise and remain high during pregnancy.