When a heifer begins the calving process in the spring, we should see what takes place in a normal delivery. This will help us better recognize problems when they occur and therefore provide assistance when necessary.
The first stage of parturition is dilation of the cervix. The normal cervix is tightly closed right up until the cervical plug is completely dissolved. In stage 1, cervical dilation begins some 4 to 24 hours before the completion of parturition. During this time the “progesterone block” is no longer present and the uterine muscles are becoming more sensitive to all factors that increase the rate and strength of contractions. At the beginning, the contractile forces primarily influence the relaxation of the cervix but uterine muscular activity is still rather quiet. Stage 1 is likely to go completely unnoticed, but there may be some behavioral differences such as isolation or discomfort. At the end of stage one, there may be come behavioral changes such as elevation of the tail, switching of the tail and increased mucous discharge. Before “pulling” a calf in stage 2, it is imperative that stage 1 (cervical dilation) is complete.