Nutrient basis conversion: dry-matter % ↔ per-1000-kcal ME
Pet-food nutrient minimums are published in two bases. Dry-matter % (DM %) expresses a nutrient as a percentage of the diet's dry matter (removes moisture distortion). Per 1000 kcal metabolisable energy (per-1000-kcal ME) expresses the amount per 1000 kcal of the diet's energy, which is the more robust basis when comparing diets of different energy density.
The 4000 kcal/kg DM assumption
AAFCO 2026 nutrient profiles state the dry-matter basis "assumes 4000 kcal ME/kg DM" (verbatim from the parsed index). Under this assumption the two bases are linked by a fixed factor.
The conversion rule (derived arithmetic)
A nutrient at X % DM = X g per 100 g DM = 10X g per kg DM. At 4000 kcal ME per kg DM, each 1000 kcal of diet contains 0.25 kg DM, so:
> nutrient per 1000 kcal ME (g) = X % DM × 2.5
(General form: per-1000-kcal = DM-value × 1000 / 4000 = ×0.25 on a per-kg basis; for % DM the per-kg figure is 10X, giving 10X × 0.25 = 2.5X. For IU/kg DM the factor is ÷4, since per-1000-kcal = (IU/kg DM) × 0.25.)
Worked examples (AAFCO 2026 dog adult maintenance, verbatim paired values)
| Nutrient | DM basis | per-1000-kcal ME basis | Check |
|---|---|---|---|
| Crude protein (min) | 18.0 % DM | 45.0 g | 18.0 × 2.5 = 45.0 ✓ |
| Calcium (min) | 0.5 % DM | 1.25 g | 0.5 × 2.5 = 1.25 ✓ |
| Phosphorus (min) | 0.4 % DM | 1.0 g | 0.4 × 2.5 = 1.0 ✓ |
| Vitamin A (min) | 5000 IU/kg DM | 1250 IU | 5000 ÷ 4 = 1250 ✓ |
All paired values are verbatim from pdf-parsed/cross_standard_nutrient_index.json (aafco_us_2026.dog_adult_maintenance DM block and its calorie_basis_g_per_1000kcal_me block); the ×2.5 / ÷4 relationship is arithmetic derived from the stated 4000 kcal/kg DM basis, not a separate source claim.
Caveat
The 4000 kcal/kg DM figure is AAFCO/FEDIAF's reference assumption for the DM↔per-1000-kcal conversion. Energy-dense or low-energy diets deviate from it, so per-1000-kcal ME is the preferred basis whenever judging "is this food enough" across products of different energy density.
Cross-references
life_stage_nutrient_matrix— AAFCO-vs-FEDIAF protein / fat / calcium / phosphorus matrix (DM %)life_stage_nutrient_matrix_vitamins— AAFCO / FEDIAF / NIAS vitamin matrix (IU/kg DM)/api/v1/cross_compare— programmatic comparison with abasisparameter (DM / cal)