Beef Cattle Calving Stages

      We normally think of beef cattle calving stages to be divided into three general  stages, preparatory, fetal expulsion and expulsion of the placenta or afterbirth. The time interval of each stage varies among types and breeds of beef cattle and among individuals of the same breed. Although the exact stimulus that initiates parturition is unknown, it does involve hormonal changes in both the cow and fetus as well as mechanical and neural stimulation in the uterus.

     A general understanding of the birth process is important to proper calving assistance and, therefore, is presented here and summarized in Table 1.

Table 1
Stages of calving

Figure 2
Normal positions of the calf just prior to delivery

      In the preparatory stage, the cervix dilates and rhythmic contractions of the uterus begin. Initially, contractions occur at about 15-minute intervals. As labor progresses, they become more frequent until they occur every few minutes. These contractions begin at the back of the uterine horn and continue toward the cervix, forcing the fetus outward. Any unusual disturbance or stress during this period, such as excitement, may inhibit the contractions and delay calving.

     At the end of the preparatory stage the cervix expands, allowing the uterus and vagina to become a continuous canal. A portion of the placenta (water sac) is forced into the pelvis and aids in the dilation of the cervix. This water sac usually ruptures and the membranes hang from the vulva until Stage 2.

Stage 2
     Delivery (1 to 2 hours, may be longer in heifer). This stage begins when the fetus enters the birth canal and usually occurs while the cow is lying down. Uterine contractions are now about every 2 minutes and are accompanied by voluntary contractions of the diaphragm and abdominal muscles.

     Surrounded by membranes, the calf's forelegs and nose now protrude from the vulva. After the nose is exposed, the dam exerts maximum straining to push the shoulders and chest through the pelvic girdle. Once the shoulders have passed, the abdominal muscles of the calf relax and its hips and hind legs extend back to permit easier passage of the hip region.

     The calf is normally born free of fetal membranes (placenta), because they remain attached to the cotyledons or "buttons" of the uterus. This ensures an oxygen supply for the calf during birth. Upon passage through the vulva, the umbilical cord generally breaks, respiration begins, filling the lungs with air and causing the lungs to become functional.

     Delivery normally is completed in one hour or less in mature cows. Special assistance is warranted if this stage goes beyond 2 to 3 hours. First-calf heifers can take 1 to 2 hours, or longer. Proper judgement should be used so that assistance is neither too hasty, nor too slow.

Stage 3
     Cleaning (2 to 8 hours). The caruncleocotyledon, or button attachment between the uterus and placenta, relaxes and separates after parturition. The placenta is then expelled by continued uterine contractions. Cows normally expel the placenta within 2 to 8 hours.