Welcome back to another chapter in the cycle of bovine reproduction, this one is a bit heavy going but I’ll try and keep it simple. Now where we left things last time was with a very exhausted cow and a new born calf. Unfortunately for the cow her work doesn’t stop there, this week we’ll be discussing the processes involved in getting her body back to normal to help rear her calf and be ready to conceive again to continue the reproduction cycle. Thankfully, the uterus is a very well developed complex organ capable of withstanding surgeries, dramatic changes in size and structure for many years while (usually) staying perfectly functional.
The state of things post-calving
Once calving is finished, most of the placenta will be expelled from the uterus but the organ is still in a very different state to its normal size and structure. Currently the structures (caruncles) that interlock with the foetal structures (cotyledons) forming the red blotches on the placenta we spoke about before are still enlarged. Some of the afterbirth may still be present and most of all the uterus has about 80% of its volume to lose before conception can take place. There is still quite a bit of (amniotic) fluid that surrounds the calf to be expelled.
Day 0: Calving
Within 12 hours of birth (but can vary) the large section of after birth we are familiar with has been expelled after the calving. The major abdominal muscle contractions that have expelled the calf and afterbirth subside. The muscle contractions of the uterus continue but are now much weaker and irregular than during the calving process. These muscle contractions separate the foetal tissues that allow the cow to pass nutrients to her calf during gestation without letting their blood mix.
During this period the cervix rapidly reforms itself to try and close off the outside to protect the vulnerable tissues inside the uterus from contamination by the outside world. This involves strong contractions in the muscles to reduce the size of the cervix from ~30cm to ~10cm in the first day post calving, then a more protracted reduction to ~2cm to seal the cervix as the folded structure is re-established. The Uterus continues to have irregular contractions during this time reducing its volume and uncoupling the foetal membranes (afterbirth). This leads to the red blotches we see on the afterbirth at the button-like connections to the mother (placentomes) on the uterine wall. These membranes will be expelled out of the vagina as a thick fluid visible from the cow’s vulva. These fluids are made up of the broken down remnants of the calf sac and some of the uterine wall material that made up the connections to the calf during gestation. This fluid discharge (lochial discharge) will be yellowish brown with some traces of red when small amounts of blood is present, the majority of this occurs on day 2-3 but will continue on for about 8-10 days.
Fluid (lochial) discharge
With the cervix structure relatively reformed the interlocking muscle folds have reformed a canal at the base of the cervix allowing the last of the fluids to be expelled from the uterus, this will subside after about day 12. The wall of the uterus will have regenerated most of the damage that occurred during pregnancy by this stage. With muscle repair and contractions, the uterus will have reduced to ~20% of its size at calving. The button like structures (caruncles) will have flattened out with the extra material broken down and expelled, they can look red and veiny as the structure flattens down into the uterine wall and the blood vessels reduce. The body will have greatly reduced the blood flow to the uterus as it is no longer a top priority for nutrient supply now that the cow has come into milk. A lot of the muscle built up in the uterine wall to facilitate the calf will regress, further reducing the volume of the uterus. Once the extra tissues have either broken down or been reabsorbed the uterus should be down to <1kg in weight. Around day 30 the uterine wall will look back to normal.
How things look now
Although everything is not quite back to normal by day 30 it comes down to the individual cow as to what point she will be fully ready to cycle again, for now let’s talk about how things look. The cervix has reformed to its normal size ~3-5cm long and the uterus is back in shape weighing about a kilogram and being roughly 2 inches deep before splitting into the uterine horns. In theory at least, the reproductive tract can begin cycling again from about day 20-25 onwards as the uterus begins to respond to hormone signals again (which it has been fairly unresponsive to during this period known as puerperal phase). In practice it can be quite a while yet before she is capable of resuming her normal ovulation cycle depending on a lot of factors like body condition (BCS), milk production, genetic traits and illness.
We will be digging more in depth into heat and cycling in future posts, but hopefully you’ve found it interesting to find out how the cow recovers from calving and have an idea where she is at while rearing her calf. If you have any questions on this topic or suggestions for what you’d like to see discussed contact me direct at firstname.lastname@example.org, via the live chat option on this page or through our Facebook page.
All the best,