Another change which a company might not consider a downgrade is to go from
one starch source to another.  See Fox's _Biology and Disease of the
Ferret_ , second edition, nutrition chapter beginning on page 149, page
166 for a discussion of how corn can raise the urine pH above 6.4 causing
bladder stones to develop.  As you have read here recently, these are NOT a
trivial problem, so best to avoid such foods.
[Posted in FML issue 2996]