A great advantage horses have over humans is the body surface/mass ratio.
Let me explain by a simple example: The mass or volume of a body determines the heat power output due to biochemical processes we call life. Let’s assume a horse weighs five times more than a human; then a horse generates five times more heat than a human.
The heat power output must be lost to the surroundings to achieve equilibrium. That is done through the body surface, so the larger body surface the more heat will be lost. (That is why we huddle together to keep warm; it reduces the body surface exposed to the cold)
Assume the body mass is proportional to the body volume. Volume is defined in three dimensions while surface is defined in only two dimensions. So a body that has a volume that is 5 times larger has a surface that is only 2,5 times larger, given all things equal. This means that a human needs approximately twice as good insulation to feel as comfortable as a horse at the same outdoor temperature!
With other words; if we were to dress in a perfect “horse-fur-coat” and had the same body fat as a horse and we were to freeze horribly; the horse would still be warm and cozy!
But it is more to ponder about horses and how they endure the elements during the winter season, so we’ll be back soon…