For a start, I’d like to welcome you to the Moocall blog where we will be analysing all things bovine. So let’s start at the beginning with the stages of calving
Stage 1: Cervical Dilation
The first step in the calving process is cervical dilation or in simpler terms; a relaxation of the muscles keeping the uterus closed to keep the calf inside and everything else outside.
Why does this happen?
The primary trigger for this relaxation is the drop in progesterone, which we will look at in more detail in future entries but for now progesterone is the hormone that maintains pregnancy and is a large factor in triggering the changes in a cow from normal operation to gestation. Once the progesterone levels drop the uterus and cervix become much more sensitive to other hormonal changes which lead to the relaxation of the reproductive tract and starts the muscle contractions of stage 2.
When does this happen?
Typically, this stage will be 4-24 hours before the actual calving event. It is very important that the cervix is relaxed fully before the calving proper begins to prevent issues further down the line if you need to assist in the birthing process.
What will I see?
Like many things in nature the symptoms aren’t always clear but during this time the cow will generally try and isolate herself from the herd and will show signs of discomfort also known as being ‘sick’ to calve. The loosening of her pelvic muscles around the pin bones can give a sunken appearance to the area around the tail head. You may also notice increased tail activity and a mucus discharge from the vulva.
Stage 2: Foetal Expulsion (Calving)
Now down to the business end of things. Stage 2 is what we generally think of as calving. There are a large number of ways a calf can present itself and we will be discussing them in a lot more detail going forward. For the sake of easy reading let’s assume everything is going well. This stage will, from first water bag, last from less than an hour up to two hours without assistance or complications. It is generally recommended to investigate if both feet have been visible for two hours, but your own judgement plays a very big role in that decision. This is the stage where everything can go wrong and particular care plays a large role in how events unfold.
When does it happen?
After the events of stage 1 the cervix is no longer keeping the calf in and the now sensitive uterus begins contractions much more vigorously than before along with abdominal contractions which will lift and move the calf out through the cervix and into the outside world. In practical terms this stage begins when the mucosal membranes are expelled or the first bag shows and ends when the calf is extracted from the cow, whether normally or surgically.
What will I see?
Hopefully, everything is going as planned and you will see evidence of a water bag (allantochorion) behind the cow followed within the next hour by a second bag (amnion) which will contain the calf head and two front legs if the calf is aligned properly. The abdominal muscle contractions and uterine contractions will gradually move the calf through the cervix and out through the vulva. The calf should present head over forelimbs with the forelimbs extended (shown below). The calf should begin taking in air and clearing mucus from the lungs during the birth process once the head and ribs are clear of the cervix. Once they are out of the vulva the movement of the cow should break the umbilical cord and you’ll have a brand new member of the herd.
Stage 3: Placental Expulsion (Afterbirth)
Now that the calf is out, some of our work is done but the cow needs to finish the process by expelling the rest of the material required to maintain a calf through pregnancy.
When does it happen?
Generally, the cow will expel the uterine contents in 4-12 hours after the birth, depending on the difficulty of the birth and any issues that may cause retention. Once this stage is complete the calving process is technically complete, the cow has a lot more work to do before she is fully back to normal.
Why does it happen?
The uterine contractions that expelled the calf will continue to expel the mucosal membranes as the internal connections between the calf membranes and the cows uterine wall have broken down separating the structures. Nature has evolved the cow to set up a complex structure to take care of the calf during gestation and once it’s no longer needed it’s a better use of energy to expel the membranes than to maintain them for future pregnancies.
What will I see?
Much of the membranes that made up the water bags we saw earlier are still within the cow and these will present in much the same way hanging from the vulva until finally coming away in one large structure. There will be large roughly circular blotches (cotyledon) on the membrane (allantochorion) where the embryo fused with the cow and allowed the exchange of nutrients to build the calf from a few cells to the animal we see before us.
You may see the cow determined to eat the afterbirth, the accepted theory on why they do this is as a prey animal it is a good survival strategy to hide away from carnivores. With all the blood and fluids involved predators would be drawn to the birth already but afterbirth can take quite a while to decompose so it is safer for the cow to destroy the evidence on instinct to help her and her vulnerable calf to hide their presence.
Hopefully, you found this interesting and informative. If you have anything you’d like to see discussed or any questions on what I’ve covered you can contact me via email at firstname.lastname@example.org or via the live chat option on the bottom right of this page.
All the best,