Bovine parturition is a three-stage procedure that includes the dilatation of the cervix, the delivery of the calf, and the placenta or afterbirth. The choice to help a female during calving is based on the birth process, typical Stage 2 timings, and the calf fetus’ usual appearance.
Intervening in the calving process too early or too late might have detrimental consequences, such as slowing contractions and delaying calving. It is critical to let the natural birth process to take its course before interfering, since waiting too long might result in debilitated or dead calves.
Starting the clock upon the appearance of the water bag at the start of Stage 2 is critical. Every few minutes, the uterus contracts, followed by contractions of the diaphragm and abdominal muscles. The calf’s front feet and potentially nose emerge from the vulva, and the dam applies maximal force to drive the shoulders and chest through the pelvic girdle. After passing through the vulva, the abdominal muscles relax and the hips and legs stretch back, making it simpler to pass through the hip area.
According to recent studies, healthy heifers and cows should calve independently within 60 minutes following the development of the water bag, whereas healthy cows normally calve in less than 30 minutes after Stage 2 begins.
Deciding whether to give aid requires judgment, and excellent judgment comes with experience. Uncertainty might develop while watching a heifer or cow with an odd appearance or a big calf. If you don’t know when Stage Two began, no progress is being made, or all symptoms are normal but the deadlines are running out, a vaginal exam may be required to establish the issue and if assistance is required.
Reference: https://fyi.extension.wisc.edu/wbic/files/2011/03/3-Stages-of-Parturition3.pdf
