I would definitely subdivide that 10 acres and rotationally graze to maximize your carrying capacity.   In SW IA you may be amazed at how many calves you can support if you get some timely rains.

I am not sure 400 pounders are ready for a straight grass diet. Rumens are not fully developed yet.  Putting out some Mineral-lyx or similar barrels for grazing cattle may help. Good idea. Use some otherwise wasted acres to raise some protein and make some $$.

Jim