AAFCO definition and what distinguishes MBM from related ingredients
Per AAFCO 2024 Official Publication ingredient definition 9.40, meat and bone meal is “the rendered product from mammal tissues, including bone, exclusive of any added blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents, except in such amounts as may occur unavoidably in good processing practices.” The definition further specifies a minimum 4% phosphorus content and a calcium-to-phosphorus ratio not greater than 2.2:1, with crude protein not less than 50% on a dry-matter basis.
MBM differs from related rendered-protein ingredients in three ways. Meat meal (AAFCO 9.41) is rendered mammal tissue exclusive of bone — no minimum phosphorus requirement, lower ash content, higher protein density. Bone meal is rendered bone with minimal soft tissue — very high mineral content, used as a calcium-phosphorus supplement rather than a primary protein source. Animal by-product meal (AAFCO 9.46) has a broader allowable input list including organ tissues but excluding hair, hoof, horn, hide trimmings, manure, and stomach contents. See our animal by-product meal explainer for that companion definition and chicken meal explainer for the named-species contrast.
The rendering process and what it produces
Per Aldrich 2006 (Petfood Industry) rendering review, MBM is produced through wet rendering: raw mammal tissue including bone is ground, heated to 115–145°C for 30–90 minutes (which separates fat, water, and protein-mineral solids), pressed to remove fat and moisture, and then dried and ground to a meal. The fat fraction becomes tallow or animal fat (a separate AAFCO ingredient). The protein-mineral solids become MBM. Typical yield is approximately 30–35 kg of MBM and 12–15 kg of tallow per 100 kg of raw input.
The rendering temperature destroys most bacterial pathogens (Salmonella, E. coli) and degrades enzymes that could compromise shelf life. Per Aldrich 2006, the temperature is not sufficient to destroy prion proteins (the BSE pathogen) — which is why FDA and EU regulations focus on input-stream restrictions rather than thermal processing for ruminant-to-ruminant prion control. The rendering process is also why MBM is often described as a “concentrated” protein source: the moisture and fat removal concentrates protein and minerals from approximately 18–22% protein in raw mammal tissue to 50–55% protein in the finished meal.
FDA 21 CFR 589 BSE Feed Ban and what it does
Per FDA 21 CFR 589.2000 (effective 1997, expanded 2008), ruminant-derived protein (including MBM, meat meal, and bone meal from cattle, sheep, and goats) is prohibited from feed for other ruminants. The regulation is the U.S. response to the bovine spongiform encephalopathy (BSE) outbreak in the U.K. and the demonstrated ruminant-to-ruminant transmission pathway. Per FDA Compliance Policy Guide 690.300 (2004) and the 2008 Specified Risk Material rule, brain and spinal cord from cattle 30 months and older cannot enter any animal-feed stream (including pet food).
Pet food is permitted to use ruminant MBM under the regulation because the BSE concern is ruminant-to-ruminant prion amplification, not dog or cat exposure (per USDA APHIS BSE risk assessments, the canine and feline BSE-susceptibility profile is much lower than ruminants). The regulatory restrictions on input streams — combined with rendering temperature and post-rendering testing — produce a regulated supply chain that pet food formulators can use with reasonable safety assurance. Per FDA-CVM, no canine or feline BSE case has been associated with U.S. pet food MBM since the regulation took effect.
Mineral profile and nutritional role
Per Camire 1990 (J Anim Sci) and AAFCO 2024 reference data, typical MBM composition is approximately 50–55% crude protein, 8–12% fat, 28–35% ash (the bone-mineral fraction), and 4–8% moisture on an as-fed basis. The high ash content is the defining characteristic: per AAFCO 2024, MBM must deliver at least 4% phosphorus and a Ca:P ratio not greater than 2.2:1. This translates to approximately 8–15% calcium and 4–7% phosphorus on an as-fed basis — substantially higher than chicken meal (3–5% calcium, 2–3% phosphorus) or salmon meal (2–4% calcium, 1.5–2.5% phosphorus).
The high mineral load is an asset for some formulations and a liability for others. For adult-maintenance and growth diets, MBM contributes calcium and phosphorus that would otherwise need supplemental dicalcium phosphate or bone meal. For senior dogs with chronic kidney disease (per IRIS 2023 staging) where phosphorus restriction is the primary dietary lever, MBM is generally avoided in favor of low-phosphorus protein sources. Per Hill 1996 (J Nutr) canine ileal digestibility study, MBM digestibility is 71–81% — lower than chicken meal (87–91%) due in part to the bone-mineral fraction reducing the digestible-protein percentage. See our chicken by-product meal explainer for a related rendered-ingredient comparison.
How KibbleIQ scores meat and bone meal
The KibbleIQ Dry Kibble Rubric treats MBM as a moderate-tier rendered protein: AAFCO-defined, regulatorily controlled, and acceptable in adult-maintenance formulations — but scored below named-species meals on three dimensions. First, transparency: MBM is species-anonymous (no source mammal species declared), which limits ICADA 2015 elimination-diet traceability. A dog with confirmed beef allergy on an elimination diet trial cannot use a food with generic MBM because the source species is not knowable from the label. Second, ash and digestibility: at 28–35% ash and 71–81% canine ileal digestibility per Hill 1996, MBM delivers less digestible protein per kg of ingredient than named-species meals. Third, supply-stream variability: per Aldrich 2006, the input streams to MBM rendering are more variable than to named-species meals, producing more batch-to-batch protein and ash variation.
The rubric does not treat MBM as a floor-tier ingredient. AAFCO 2024 definition + FDA 21 CFR 589 oversight + rendering-temperature pathogen control put MBM well above ingredients without regulatory definitions. Foods that pair MBM with a named-species primary protein (e.g., “chicken, meat and bone meal, brown rice…”) score better than foods where MBM is the only protein source. For senior dogs and dogs with renal-disease formulations, MBM is generally not the right choice on phosphorus grounds. See best dog food for large breeds and lamb meal explainer for the named-species contrast. To check what your dog’s food contains, paste the ingredient list into the KibbleIQ analyzer.