Wild horses were never meant to run like T-breds do. Tens of thousands of years of evolution cannot be undone in a heartbeat.

The game involves horses running at very high speeds in some cases up to 2 minutes straight.
If you got all those guts coming forward on a diaphragm that is right on those huge lungs that contains massive numbers of very tiny capillaries, guts slamming into them from behind for two minutes (each time a horses front hooves hit the ground), I find it hard to believe that capillaries will not break.

I really dont know how easily this can be bred out. I dont think anyone does. If you find a horse that never bleeds and mate this to a horse that never bleeds, we cannot assume the offspring will be the same. There might be a myriad of reasons some horses might not bleed. One major reason could be because they are slow. I know the horses that run the really long course races do not bleed nearly as often if at all... horses basically gallop these courses.

We want fast horses over short distances (1 1/4 being short). Lots of inertia involved in that type of running. So lots of damage.

The horse was never meant to do what is asked of these animals, they just were not meant for this. We bred them to run, and run hard. So all sorts of consequences follow. I dont like this, but have accepted this. And I surely dont want horses being pushed on with lungs full of blood, or having to face the consequences of massive septic infection due to all the crap that might enter bleeding capillaries or grow in blood within lungs.