A Herdman's Handbook for the Modern Homesteader

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Toward the end of this initial phase of parturition the first water bag (allantois-chorion) will usually rupture as it is forced into the birth canal. This breakage generally occurs internally and is rarely observed except, possibly, as a sudden gush of fluid. Shortly after this, the second water bag (amnion) appears. The second sac is tougher than the first and may not rupture until punctured by the feet of the fetus . . . thus, this is the water bag most often noticed.

At about the time the amnion appears at the vulva, the fetus begins to enter the pelvic portion of the birth canal. The normal position of the fetus at birth is with the head and front feet extended and with the spinal column of the calf in line and next to the spinal column of the dam. The physical pressure of the feet and head being forced into the vagina initiates the next stage (active labor) or parturition.

Active labor starts with the onset of pronounced abdominal contractions or straining, and ends with the actual expulsion of the calf. The contractions are mild at first and result in the exposure of the front feet, followed shortly by the head. As the head and shoulders are being forced through the pelvic area, the abdominal contractions reach their greatest intensity . . . and, after the head and shoulders are through, the rest of the body is usually delivered quite rapidly. The time lapse for this second phase of birthing is from one-half to four hours. Here again, a heifer may take the full four hours, while an older cow will almost always deliver in an hour or less.

The third stage of delivery is not nearly so dramatic as the preceding one but is, nevertheless, very important. The membranes that surround the calf before birth (the amnion, allantois, and chorion) are collectively known as the placenta and the expulsion of this placenta is the predominant feature of the third stage. This normally occurs within eight hours of the calf's delivery, but it takes about a month for the uterus to return to a physiologically normal condition.

Parturition in most domestic animals follows a pattern similar to that outlined above for cattle. Most variations involve the time element and the number of fetuses present (see Table 2).

As you can imagine, the time of parturition is fraught with danger for both cow and calf. Two of the most common causes of dystocia (difficult birth) are: [1] a relatively large calf in relation to the size of the birth canal and [2] a situation in which the calf's position or the position of its limbs makes it impossible for the calf to be born. There are other rare causes of dystocia, but it is beyond the scope of this article to deal with them.

In the light of the preceding description of the normal birth process, it is relatively easy to catalog the more commonly observed indications of a possible dystocia. (These signs are not listed in order of importance or frequency of occurrence.)

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