Sometimes an animation can do more to help people understand a process than a drawing or a photograph.
The video explaining parturition in mares by Ghent University is a combination of live video that includes a mare in labor and giving birth, as well as animations. The animations show the foal inside the mare and it's rotation as it enters the birth canal. It also shows possible complications during birth and how they can be corrected during the birthing process.
After spending a semester studying equine reproduction I can recommend the quality of the animations along with the voice-over narration that make this video suitable for horse owners and students. Some of the illustrations we used in class were over-simplified such as showing the developing foal in a human-like uterus.
One thing that stands out immediately in this video is the foal's rear hooves being held by the gravid horn of the uterus. Unlike humans, horses and other animals have a main uterus and two uterine horns. While animals like cats and dogs that have litters where fetal development happens in the horns, the horse fetus uses one of the horns to hold the hind limbs with the head pointing towards the cervix. The second horn doesn't play a role while the foal is developing.
Horses are usually unable to carry twins due to the complex nature of the diffuse placenta and uterus being able to carry only one foal to term. When a horse does produce twins, one embryo is usually destroyed by membrane disruption since their is risk of death for the mare and one twin usually does not survive. However, live twins have been born in rare cases.
Another very specialized video on equine pregnancy diagnosis that students view as part of the course material is not available on YouTube. One of the most amazing pieces of that film included in-utero video of the developing fetus during the early part of the pregnancy. Unlike humans, the fertilized embryo does not implant on the uterine wall. This occurs later, around 40 days into the pregnancy. Until that time, the embryo bounces around the uterus and uterine horns and must come in contact with 80% of the uterine surface for maternal recognition to occur.
Today there are realistic animations available to help students and owners visualize intricate biological processes of horses. These run the gamete from reproduction to anatomy videos like "The Glass Horse" series. There are even applications available for tablets and cell phones like "Horse Anatomy 3-D." These tools help us understand the unique aspects of the horse and how we must tailor our medical treatment to suit them.