The bible said to pitch inside and out, no reason why the grain bins would not of been sealed inside and out, thus they would of been preserved from the humidity. Grains energy value compared to huge volumes of hay reduced the size needed for energy storage (condensed energy) add water an serve.
Besides the fact that you responded to the wrong post - mine was simply a question as to which YEC author came up with the idea of pelletized, dehydrated grain (I'm pretty sure now that I think about it that it was Woodmorappe) - your "response" yields a whole raft of new questions.
Are you aware of the humidity problem on all ships, let alone wooden ones? It has nothing to do with calking/pitch - which has to be renewed periodically regardless of how well applied. The very
air is saturated. Modern ships have substantial mechanical dehydrators to insure their cargo holds are relatively humidity-free. No matter how well "pitched" the Ark was, there was no possible way to reduce the moisture content of the air itself. Now, picture a bunch of pitch-coated bins filled with highly absorbant grain on a wooden ship in the midst of the mother-of-all-storms. What do you figure the saturated air will do? Can you say "mold heaven"? Ergot is just one of the problems...
Another issue is simply one of volume: do you have any conception of the amount of grain (and not all herbivores can digest grain very well - few of the browsers, for instance, have the appropriate gut fermentation capability) required for even a very small number of large herbivores? For a year (or more, if all those forests, savannahs, etc, had to be replanted by hand)?
Finally, as nator mentioned, horses and others have a really hard time surviving for more than a few days on grain alone. Ever heard of "bloat"?