Cervix begins to dilate, allowing water sac to protrude. 2 to 6 hours 2. Fetal Expulsion Cow usually lies down and fetal contractions begin. Fetus enters birth canal. Front feet and head protrude first.
Calf is delivered.
1 hour or less 3. Uterine contractions expel membranes. Correct positioning of the calf as it enters the birth canal stimulates contractions of the diaphragm and straining of the abdominal muscles, which presses the head and feet of the calf against the cervix, causing it to relax and open. If a cow shows signs of stage 1, but does not exhibit the straining associated with stage 2, check the position of the calf. As the calf continues through the birth canal and into the vagina, the water bag ruptures and the front feet appear first, hooves down, if positioned correctly.