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]