Meat and bone meal is not a commodity in the way that soybeans or corn are. Two bags labeled “MBM 50% protein” from two different suppliers can perform completely differently in a feed formulation — one supporting healthy animal growth, the other quietly dragging down feed conversion ratios and costing far more than the price difference between them.
The quality variation in MBM is wide, real, and largely invisible on a standard product sheet.
Why MBM Quality Varies So Much
MBM is a rendered by-product. What goes into the cooker determines what comes out, and rendering plants process a constantly shifting mix of raw material from slaughterhouses — bones, trimmings, organs, connective tissue — in proportions that change with season, animal availability, and the economics of the processing facility.
Unlike a manufactured ingredient with a fixed recipe, MBM composition reflects the raw material blend on any given production run. A batch with a high proportion of bone will have more ash, less digestible protein, and a different amino acid profile than one with a higher proportion of soft tissue. Both can be sold as “MBM.” Both can carry the same headline protein figure on a certificate of analysis if the COA only tests crude protein and moisture.
This variability is the core of the quality problem. Knowing what to test for — and what numbers to reject — is the practical skill that separates experienced MBM buyers from ones who get burned.
1: Crude Protein Is High But Ash Is Also High
The single most important relationship in MBM quality is the inverse link between protein content and ash content. More bone in the raw material means more ash and less digestible protein. This is not a problem in itself — it is how MBM works. The problem comes when suppliers manage the headline protein figure upward without disclosing what else is in the product.
A COA showing 50% crude protein alongside 38–40% ash should prompt immediate questions. Standard commercial MBM has ash in the range of 28–35%. When ash climbs above 35%, the bone fraction is high enough to meaningfully reduce the amino acid digestibility of the meal — the protein that looks good on paper is increasingly collagen-bound, mineral-diluted, and nutritionally less available to the animal.
What to check: Always ask for both crude protein and ash on the same COA. Request the Ca:P ratio as well — it should sit close to 2:1, reflecting natural bone mineral proportions. A Ca:P ratio significantly above 2.2:1 is a classic signal that limestone or calcium carbonate has been added to inflate apparent mineral content without contributing nutritional value.
2: Pepsin Digestibility Is Not Reported
Crude protein measures the nitrogen content of a sample and multiplies by a conversion factor. It does not tell you how much of that protein an animal can actually absorb. For MBM, the relevant measure is pepsin digestibility — a lab test that simulates gastric digestion and reports what fraction of the protein is soluble and available.
Good quality MBM from properly rendered soft-tissue-rich material will show pepsin digestibility of 85% or above. Overheated material — where excessive temperature or pressure during rendering has cross-linked proteins and degraded amino acids — can fall to 70% or below. A batch that tests at 68% pepsin digestibility and 50% crude protein is nutritionally a very different ingredient from one at 88% digestibility and 48% crude protein, even though the first looks better on a simple protein label.
Overheating is a common quality failure in MBM production. It occurs when rendering temperatures or dwell times exceed the point needed for sterilization, continuing into ranges where lysine and cystine — the first limiting amino acids in MBM-based diets — begin to degrade. You cannot detect overheating by looking at the product. Pepsin digestibility testing, and ideally a reactive lysine assay, is the only reliable way to catch it.
What to check: Require pepsin digestibility (minimum 85%) in your specification. For high-inclusion applications, ask for amino acid profile data, particularly lysine and methionine. Any supplier unable or unwilling to provide this data on a per-batch basis is operating below the standard you should accept.
3: Color and Odor Are Off
Physical inspection is not a substitute for lab analysis, but it provides a rapid first filter that experienced buyers use before any testing is conducted.
Good quality MBM is a coarse to fine brown-to-tan meal with a consistent, mildly meaty odor. It should be dry to the touch with no clumping, no surface moisture, and no evidence of mold.
Problem batches often present in one of several ways:
Dark brown to black coloration indicates overheating during rendering or drying. The Maillard reaction — the same browning that occurs when meat is cooked too long — reduces the bioavailability of lysine in particular. A batch that is notably darker than your reference standard should be tested before use, not accepted on the strength of the COA alone.
Rancid or sour odor indicates oxidation of the fat fraction, either from excessive fat content in the original render or from inadequate drying and storage after production. MBM with rancid fat will reduce palatability in finished feed and may introduce oxidative stress in animals at higher inclusion rates.
Clumping or surface moisture suggests either inadequate drying to specification or moisture absorption during transport or storage. MBM above 10% moisture is outside standard specification and is susceptible to bacterial growth and mycotoxin development.
Unusual pale or white areas in the meal can indicate high proportions of bone flour or, in the worst cases, limestone or other mineral adulterants introduced to boost apparent calcium content.
4: The Ca:P Ratio Is Off
This one catches a specific and well-documented form of adulteration. Limestone (calcium carbonate) is cheap, abundant, and raises the apparent calcium content of a product when added to MBM. It contains no phosphorus and contributes nothing to protein nutrition.
Natural bone mineral — hydroxyapatite — has a calcium to phosphorus ratio of approximately 2:1 by weight. Legitimate MBM, even with significant ash content, should maintain a Ca:P ratio close to this natural value. When limestone has been added, calcium rises disproportionately while phosphorus stays flat, pushing the Ca:P ratio noticeably above 2.2:1.
A routine check: divide the reported calcium percentage by the reported phosphorus percentage. If the result is above 2.3–2.5, request an explanation and consider third-party verification testing before accepting the shipment.
5: Inconsistent Batch-to-Batch Specifications
A single COA from a single batch tells you almost nothing about what you will receive across a supply relationship. The meaningful quality question is not “what did this batch test at?” but “how much does this supplier’s product vary across batches, and within what range?”
Reputable suppliers can provide multi-batch COA history — at minimum ten consecutive production batches — showing the range and standard deviation of crude protein, ash, moisture, and fat. A supplier whose protein content varies from 44% to 58% across batches is not providing a specifiable ingredient. A supplier holding 48–52% protein with ash consistently at 30–33% is.
Request this history before placing a first order. If a supplier cannot or will not produce it, treat this as a serious quality signal.
6: Species-of-Origin Is Not Declared Per Batch
This matters for two reasons: regulatory compliance and nutritional consistency.
On the regulatory side, porcine, bovine, and mixed-mammalian MBM carry different permissions in feed applications under EU and other market regulations. A supplier who cannot specify species of origin on a per-batch basis cannot support your compliance documentation.
On the nutritional side, bovine and porcine MBM have somewhat different amino acid profiles and fat compositions. Mixed-source material without species segregation introduces variability that is difficult to manage in a tight feed formulation. Knowing what you are buying — and receiving consistent documentation that confirms it — is a baseline requirement for professional feed procurement.
What a Reliable COA Should Include
When you request documentation from a supplier, a minimum specification-grade COA for MBM should report:
- Crude protein (%)
- Moisture (%)
- Crude fat (%)
- Ash (%)
- Calcium (%)
- Phosphorus (%)
- Ca:P ratio
- Pepsin digestibility (%)
- Salmonella (negative per batch)
- Species of origin declaration
Some applications will additionally require amino acid profile (lysine, methionine, cystine at minimum), heavy metals panel, and dioxin/PCB analysis depending on the destination market’s regulations.
A COA that only shows protein and moisture is not a quality document. It is a label.
The Practical Takeaway
Low-quality MBM is not always the cheapest option on a per-tonne basis. Sometimes it is priced competitively with specification-grade material, because the quality shortfall is invisible until it shows up in animal performance data weeks after the batch has been consumed.
The protection against this is not more price negotiation. It is better specification enforcement: require pepsin digestibility, require full ash and mineral data with Ca:P ratio, require multi-batch COA history before the first order, and require species-of-origin declaration per shipment. Suppliers who meet these requirements routinely are operating to a different standard than those who cannot.
Need specification-grade MBM with full batch documentation? Contact our team to discuss quality requirements and supply availability.