A few years ago I was responding to a question on a horseman list on the internet. In response to one particular question I made an inadvertent and off-the-cuff remark to the effect that it wasn't my desire to have my horse "plodding around like an old packhorse." This seems to have raised the hackles of at least one subscriber and a long letter was sent to me by e-mail. I have inserted the letter below for the benefit of those who (like me) have an interest in packhorses.
The True Horse Person
Coat Shedding
It evolved that horses are more comfortable at colder temperatures than warmer ones. Their thermal neutral temperature range varies between 5 and 12 deg C. Whereas humans have a comfortable temperature around 20-22 deg C. I won’t go into how this works, but the way a horse’s coat grows is part of the mechanism. It also helps that horses primarily breathe through their nose and not their mouth when it comes to reducing heat loss.