Normal Birth Process for Cows

Stage 1 – Dilation of the cervix

In general, this stage lasts from two to three hours in mature cows and four to six hours in heifers.

During this stage, the cervix dilates because of the release of a hormone (oxytocin) and the pressure of the "water bag" against it.

Thus, early breakage of the "water bag" may delay the normal dilation of the cervix.

The cervix is closed at the beginning of stage 1 (A) but begins to dilate throughout this stage, allowing the fetus to enter the birth canal (B).

Stage 2 – Delivery of the calf

The second stage is characterized by the progression of the calf through the birth canal and its expulsion.

At this stage, the calf may still be enclosed in the second "water bag" (amniotic fluid).

After the head has passed through the birth canal, the rest of the body usually demands little extra effort to be expelled.

This stage may last from two to 10 hours.

A common mistake is to attempt to assist by pulling on the forelegs of the calf unnecessarily or too early.

Stage 3 – Expulsion of the placenta

During the third stage, the placenta or afterbirth is expelled from the uterus.

After the delivery of the calf, uterine contractions continue for a period of time.

These contractions help to break down the cotyledons by separating the placenta from the uterine caruncles.

Normally, the afterbirth should be expelled within 12 hours of birth.