I'm no farmer, but seems to me that the corn goes in one of the cow and out the other end. You put that back where came and it builds up over time. You also grow soy to put nitrogen back into the soil.
Corn farmers typically don’t raise cows anymore.
And there are places in West Texas that went from red dirt to black because of cattle.
In Wisconsin, cow manure is NO LONGER ALLOWED to be put back onto the land. It is put into tanks as slurry & trucked AWAY from the farm...... INSANITY