[QUOTE=zipperfoot;8062528]
Interesting points, esp with regard to carnivores/herbivores. When I posted, I was in a hurry and probably didn’t make my point clearly, which was that rigidity of the spine most likely doesn’t enhance speed in horses. Rather, horses are fast DESPITE their rigid spines.
Interesting sidelight on cheetahs: they’re totally designed for SPEED–skeletal structure, muscle fiber type/distribution, cardiovascular system, even the shape of the head. Running is ALL they do and they’re superbly designed for it. Horses have some of these adaptations, but not to the same extent.[/QUOTE]
I think the mechanism for speed in horses is much different than it is in cats. I read a couple of studies on the biomechanics of the gallop in horses , one on the function of the muscles and structure of the neck and another that discussed the swing of the leg , speed and relative lengtht of leg bones, I am sure I will never find them now but if I do I will link them.
Any way, the ossilation of the neck contributes greatly to a horses speed at a gallop and the muscles are used to Co troll the effect of the weight of the head at the end of a long thin neck. Maybe the ossilation of the back in cheetahs has the same function.
The conclusion of the second study was that mechanically the fastest structure of the limb in horses was a long thin cannon bone which explains a lot about your modern thoroughbred. Of course, that structure may be the fastest but it isn’t the best for weight bearing so if you were to breed a sounder TB with a shorter cannon you would likely be sacrificing speed.
It sounds like the same situation with your jumping horses where adding a different breed may compromise the mechanics of the jump, but maybe for a similar benefit in the long term?