Wis. Admin. Code § ATCP 42.40 – Statement of calorie content.

The label of a dog or cat food may include a statement of calorie content only if all of the following apply:

(1) The statement is separate and distinct from the guaranteed analysis under s. ATCP 42.30.
(2) The statement appears under the heading “Calorie Content.”
(3) The statement reflects metabolizable energy, expressed as “kilocalories per kilogram” of dog or cat food. The amount of metabolizable energy may also be expressed in kilocalories per unit of weight or measure used in the declaration of net quantity under s. ATCP 42.28 (1) (h) or the feeding instructions under s. ATCP 42.38.
(4) The calorie content is determined by one of the following methods:
1. (a) By calculation using the modified Atwater formula, ME(kcal/kg) = 10[(3.5 x CP) + (8.5 x CF) + (3.5 x NFE)], where CP = % crude protein as fed, CF = % crude fat as fed, NFE = % nitrogen-free extract (carbohydrate) as fed, the percentages of CP and CF are the arithmetic averages obtained from proximate analyses of at least four production batches of the dog or cat food, and NFE is 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).
2. (b) By a testing procedure published in the 2018 Official Publication of the Association of American Feed Control Officials.
  Note: Copies of the Official Publication of the Association of American Feed Control Officials are on file with the department and the legislative reference bureau. Paper or electronic copies may be obtained from AAFCO at www.aafco.org.