Remembering that the first stage of labor prepares the cow for active calving. The reproductive tract becomes lubricated and softened as rhythmic uterine contractions bring the calf up into the vaginal vault. The conical pressure created by the calf signals the start of the second stage of parturition. Contact and pressure by the calf stimulates the final dilation and thinning of the cervix. Now, the real work for the cow begins.
A textbook definition of stage two labor is obscure, but always includes the active expulsion of the fetus. The amnion or calf membranes appear at the opening of the vulva. The uterine contractions become increasingly rhythmic and closer together. At some point, her water breaks. The cow lays down and begins to abdominally push. She may roll completely on her side to deliver her calf. Both front feet and the head of the calf will come through the reproductive tract in the anterior position. One front leg will be slightly ahead of the other, in an aerodynamic move to bring the shoulders through the pelvis at their narrowest advantage. The nose will be nestled just behind the fetlocks. Once the calf’s head and shoulders are out, its body will naturally rotate to free up the hips, allowing the rest of the calf to be delivered. The cow should complete stage two within 30 minutes or so. Each hard abdominal press results in measured progress as the hooves inch out a little at a time. Heifers may take a bit longer to loosen up the vaginal vault, with active calving completed in about an hour.
Once the abdominal compressions of stage two begin we are watching our cows very closely to monitor progress. Failure to progress is the hallmark of dystocia, or calving difficulty. If two feet are showing at a constant distance outside of the vulva and the nose fails to appear after a dozen hard abdominal pushes or 20 minutes, I intervene. I will not give a cow an hour if she is not progressing with aggressive attempts. The following scenarios are common reasons that cows require calving assistance in stage two and are defined by what is showing outside of the vulva during her attempted calving.
In a fetal:maternal mismatch the size of the calf and the size of the pelvic opening of the cow are not compatible. The three necessary parts, two legs and a head, will struggle to fit into the vaginal vault at the same time. Sadly, one or more of the parts will often drop out of the race, defining a whole class of calving difficulties.
- Simple dystocia - If the calf is simply too large for the dam’s pelvic opening, the calf is considered undeliverable vaginally and a C-section will be ordered. The head combined with the two front legs are the limiting factor. However, if they can fit through the pelvic opening, the rest of the calf can make it as well.
- Leg back - one foot and a nose showing is the most commonmalposition that I get called out to attend. A full size, full term calf cannot be delivered in this position. If detected early, the dropped leg can be brought up and delivery of the calf can be attempted. The overwhelming majority of these dystocias result in a positive outcome, even if a C-section is required.
- Head with no feet – Seeing only a head protruding from the vulva can be very scary. Due to the conical shape of the head and the even pressure it exudes, these cows are typically in full second stage labor and pushing like crazy. An epidural can quiet the pushing enough to retract a washed head back into the cow to assess whether or not the two legs can be eased into the vaginal vault with the head to make it out of the vulva.
- Two feet and no nose is luckily, not a common stage two problem that I get called out to attend. Again, we are having an issue of all three necessary parts not making it into the vaginal vault. This can certainly be caused by a fetal:maternal mismatch, where the head gets denied because the large feet and legs are occupying the lion’s share of the available space. However, there is often another sad determining factor. If the calf has died prior to the onset of stage two, the lack of muscle tone in the calf can result in a limp neck that can easily fold back, typically over one shoulder.
- Upside down feet rarely signify an upside-down calf. If the calf is upside-down, the cow needs to be examined for a uterine torsion. These calves are rotated to the anterior position and delivered accordingly. Typically, the calf is coming backwards, called the posterior presentation. There are serious complications stemming from the back feet heading out first versus the front feet. The rear legs taper quickly to a broad rump, lacking the ideal gradual conical shape of the calf’s front end required for optimal dilation of the reproductive tract. Labor can be delayed for improper dilation and the cow is at greater risk for cervical damage and tears. Compounding problems, once the umbilical cord of a backwards calf reaches the pelvic brim (usually once the thighs have been delivered), it will be compressed. Compression stops the blood flow to the backwards calf which results in a signal for the calf to take her first breath. Unfortunately, her head is down inside a vat of amniotic fluid. If she isn’t promptly delivered, she will take fluid into the lungs and possibly succumb to immediate drowning, or respiratory failure over the first 72 hours of life. If she is quickly extracted, her first breath will be taken outside of the cow. These calves should always be aggressively assisted.
- Breech calves are actually kind of fun to correct. Cows can have trouble with a breech calf in either stage one or stage two. Often, due to the uneven pressure from a larger calf’s awkwardly shaped rear end, the cow may never actually go into stage two of parturition. These cows are frequently caught trying to claim another cow’s calf as she’s hormonally ready to mother up. If the calf is small enough, the pin bones of the hips may be directed far enough into the vaginal vault to initiate pushing. The calf’s tail may dangle from the vulva with the rear legs tucked in under the calf’s belly.
Stage two dystocias are pretty easy to spot, considering the cow is typically laying down, actively pushing and showing some parts of the calf at the vulvar opening. A delivery with a normal presentation and healthy progression often go unnoticed since they happen so quickly. On the flip side, determining when the presentation is abnormal or when the cow fails to progress will take a bit more scrutiny. Recognizing abnormalities quickly will facilitate prompt help for both the cow and the calf, leading to better outcomes.
About the Author
Dr. Colleen Lewis is a 1996 graduate of Kansas State University, College of Veterinary Medicine. Her career has taken her to many places as a practice owner, consultant, embryologist, and mentor. She enjoys mixed animal practice, teaching, traveling, farming and high school sports with her husband, Andrew and their three boys.