Figure 1. Relationship between measured metabolizable energy (ME) concentrations (x-axis) and ME concentrations predicted using equations with modified Atwater factors [4] (y-axis) for dog and cat pet foods.

The modified Atwater factors are 3.5 kcal/g for protein and carbohydrate, and 8.5 kcal/g for fat. Ideally, all points should be on the line x = y. A) Measured ME concentrations were determined from 331 total digestibility studies in dogs, of which 259 used dry dog foods and 72 used canned dog foods. B) Measured ME concentrations were determined from 227 total digestibility studies in cats, of which 173 used dry cat foods and 54 used canned cat foods.