U_Stormcrow
Crossing the Road
@U_Stormcrow Thank you for the explanation, except you have a statement in your post which surprised me: "Rice, of course, is even more deficient, and is still nutritionally superior to corn". According to the table above corn is better than rice? or I am missing something, I guess - rice or corn?
Sources matter, Maiahr, and in the source I choose to use (Feedipedia.org), Rice {Brown Rice , Broken/White , Rough/Paddy} is (marginally) better than Corn. (Click on the "Nutritional Aspects" and "Nutritional Tables" tabs)
As you can see from comparing the various rice I linked, how its preparred matters - removing the hulls helps greatly improve digestibilitiy and reduces the fiber content substantially.
Here is brown rice - Look at where I circled - in tests, the crude protein varied from a low of 7.5% to a high of 14.5%. The average was 10.5%
Here is the same table for European Corn: (Lower low, lower average, lower high - even adjusting for the higher average water content)
and if your corn is sourced from North Africa??? Its inferior to the average European Corn (though more consistent)
THAT is why I said rice was marginally superior. We can do the same thing with key amino acids. and that's before considering specialties like "golden rice" with its improved vitamin profile (too expensive to feed chickens, anyways).
Thanks for asking!