I found this article on the net about breeding heat tolerant sheep. Interesting.....
" Ron Parker in The Sheep Book discusses a program wherein a Professor Leroy Boyd of Mississippi State University attempted to develop sheep that would be adapted to the hot and humid conditions of the deep South. He noted that "animals with greater development in the loin and rump, thicker skin, and deep rather than wide bodies tended to have a greater heat tolerance." (p. 87) If this is true, then continuing to improve your sheep's conformation for these traits may help create a more heat-tolerant flock. "
I also read where thicker skin on cattle make a difference in heat tolerance.
wasn't the arabian horse bred to be heat tolerant?