Except as required in 42.8(198), the label of a dog or cat food may bear a statement of calorie content, provided:
where CP = % crude protein as fed
CF = % crude fat as fed
NFE = % nitrogen free extract (carbobydrate) as fed and the percentages of CP and CF are the arithmetic averages from proximate analyses of at least four production batches of the product, and the NFE is calculated as the difference between 100 and the sum of CP, CF, and the percentages of crude fiber, moisture and ash (determined in the same manner as CP and CF). The results of all the analyses used in the calculation must acCornpany the affidavit, and the claim on the label or other labeling must be followed parenthetically by the word "calculated"; or
Iowa Admin. Code r. 21-42.7