The most popular methods for calculating gestational age are biparietal diameter (BPD) and crown-rump length (CRL). Gestational sac measurements are not well validated or easy to perform in goats. There are also qualitative methods you can use, such as the size of the cotyledons. This calculator uses the BPD method, because it’s well validated in a number of goat breeds from 6 weeks gestation.
Here, our obstetric sonographer Yvette Lovis demonstrates how to obtain an on-axis image of a skull in a dog. The principle is exactly the same in goats:
If you need help learning where to place your caliper points to perform this measurement accurately, you can take our course, get a copy of this book (but bear in mind the focus is on canine pregnancy), or join our AI project (details at the bottom of the page).
BPD for gestational age estimation
The below calculator is based off published adjustment values that I’ve taken from scientific papers. Unfortunately, nothing is published for many of your favorite breeds, like Nigerians, Lamanchas or Alpines. Try and find the closest equivalent to your breed for now, and let’s work together to fill in the gaps. Keep records of your measurements and when your goat kids; if you find, for example, that your goats consistently kid four days earlier than the predicted date on this calculator, we can add in our own adjustments.
Invitation to collaborate
I am working on training AI to recognise pregnancies and calculate gestational age. There is very little funding out there for research in goats, but my wonderful Professor has given me permission to use the systems I develop for my funded human cardiology research, and adapt it for this purpose (as long as I do so in my own time). If you regularly save images and videos (or can get into the habit of doing so) and would like to be involved, please let me know. It doesn’t matter if your machine costs $500 or $50,000. All that matters is that you save images and/or cine loops directly to your machine, and export them. All images will be kept confidential, and will not be shared without your permission. If you would like to be involved, you can contact me, Catherine Stowell, or join our project’s Facebook group here.
If you need help exporting images off your machine, just ask.