Synchronizing object takes too long Im currently doing an animation.

One object in my scene has 1million polygons and highres textures.

Just synchronizing the object, during rendering  takes 30 sek.
So with 240 frames, each test-render of the entire animation, takes at least 2 hours. 

Without the heavy poly-object it just takes 3 sek per frame.

Why does Blender need to synchronize the entire scene, for each frame of an aniamtion. And can't just do it once ?
Especially when certain objects don't move.

And is there a way to do this just once ?
Create a low poly mesh resembling the high poly mesh, intersect both, bake them and apply the obtained texture to the low poly mesh.