The new year means the start of a new calving season for many producers. A key for any producer planning for a successful calving season is an awareness of the signs and length of the different stages of labor for cows and heifers. In this article I will discuss the different stages of labor and will continue with additional articles on why and when intervention should occur.
During stage one of labor, the cow or heifer will distance herself from the herd, showing signs of restlessness and a tendency to lie down and get up frequently. These signs are often more apparent in first-calf heifers than they are in mature cows. In this stage, coordinated uterine contractions begin. These contractions increase from a rate of one every 15 minutes to on every three minutes by the end of stage one. Keep in mind that, even though these contractions are usually not outwardly visible, a period of oxygen deprivation in the placental attachments takes place with every one of them. It is in this stage that the first water sac (chorioallantoic membrane) breaks. The length of this stage should last around 2-6 hours. If this stage of labor is prolonged, the decrease in bloodflow and oxygen from repeated uterine contractions may start to adversely affect the survival of the fetus. When a stillborn calf is delivered, it is often the result of prolonged stage one labor and the failure of the cow or heifer to progress to stage 2.
The second stage of labor occurs when the cervix is fully dilated and the second water sac and fetal parts enter the birth canal, eventually becoming visible to the observer. The cow is visibly contracting the muscles of her abdomen in an effort to push the calf through the birth canal. The first significant effort occurs in pushing the head through the cow’s vulva, then a secondary effort helps push the chest through. It is at this point that the cow will often take a short pause, allowing the calf to take its first breath of air, which is important since now the calf’s umbilical cord is compressed within the birth canal. It’s after this that the hips are expelled and the calf is fully delivered. Stage 2 normally can last from 30 minutes to 2 hours.
The final stage, stage 3, is the passing of the placenta, which typically occurs within 8-12 hours. Most veterinarians, however, do not recommend treatment or removal of the retained placenta until 72 hours after calving, or if the cow is showing outward signs of illness. Early or aggressive attempts at removal or other interventions often result in more harm than help to the cow.
Knowing the stages of labor is the first step in trying to decide when and how to help heifers and cows experiencing difficult calvings. In next week’s iGrow Beef article, the signs of the distressed calf will be discussed, along with the situations in which cattle producers should actively intervene in a calving situation.