MBM IN CHICKEN DIETS: PRACTICAL NUTRITION, MEASURABLE BENEFITS, AND MANAGEABLE RISKS. FEED FORMULATIONS FOR ALL PHASES

Meat and bone meal with ~50% crude protein is best understood as a dual-purpose ingredient. It supplies concentrated animal protein with a useful lysine contribution and highly concentrated calcium (Ca) and phosphorus (P) that can reduce reliance on limestone and inorganic phosphates when diets are carefully balanced. Its strengths – nutrient density, circularity benefits, and a mineral package aligned with bone and eggshell biology – also explain its main risks: batch variability, formulation imbalances (Ca:P and digestible amino acids), and food – safety hazards that are mostly about control systems rather than the ingredient itself (post – process contamination, oxidative rancidity, regulatory compliance). Evidence from poultry studies shows MBM can support broiler growth and layer egg production/eggshell traits when used within quality – controlled inclusion ranges, but high or poorly characterized MBM can depress performance and, in challenged broilers, may exacerbate gut – health problems linked to undigested protein (notably necrotic enteritis models). A “MBM50 works” mindset therefore starts with safety certification and analytical verification, then moves to digestible nutrient balancing and phase-appropriate inclusion, followed by close monitoring. 

WHAT MBM50 IS AND WHY IT STILL MATTERS

MBM is a rendered product made from animal tissues and bone. The bone fraction is why MBM is distinct from “meat meal,” and in practice ash (mineral matter) and phosphorus help differentiate the two (a common rule of thumb is that when P exceeds ~4.5% it is classified as meat-and-bone meal). 

When nutritionists say “MBM50,” they are typically describing a product guaranteed near 50% crude protein (not a 50% inclusion rate). In the United States, extension and industry convention often discuss MBM quality around a minimum 50% CP, with constraints on the Ca:P ratio (frequently cited as not exceeding ~2.2× total P). 

From a practical formulation standpoint, MBM50 is attractive precisely because it can replace two cost centers at once: some soybean meal protein and some mineral phosphorus (e.g., dicalcium phosphate), while also supplying calcium. Recent open – access broiler energy work explicitly frames MBM as an alternative protein – and – phosphorus source that can substitute more expensive ingredients, with potential environmental benefits through utilization of slaughter by – products. 

I emphasize this point because the “value” of MBM50 is not a single number like crude protein. Its value is the tight coupling of protein and minerals, which is biologically convenient (bone and eggshell mineralization depend on Ca and P) but mathematically unforgiving if you guess wrong about the batch. 

NUTRITIONAL VALUE AND BIOAVAILABILITY

Proximate profile and what MBM50 contributes.

A reasonable working profile for MBM50 (as-fed) is CP ~50 – 53%, fat ~9 – 12%, ash ~28 – 32%, Ca ~9 – 10%, P ~4.5 – 5.0%, with metabolizable energy that is moderate but variable. Large database summaries show ash commonly in the high – 20s to mid – 30s, with Ca and P concentrated enough that minerals can become the first limiter in some formulations. 

Two caveats matter in real feed mills:

1. Batch variability is not subtle. In a large survey of commercial MBM, crude protein, fat, ash, and amino acid digestibility varied widely; lysine and sulfur amino acid digestibility are particularly variable, and the paper’s core message is that tabulated values are risky unless batch quality is measured. 
2. High ash usually means lower protein and lower energy. Contemporary broiler metabolism work shows MBM lots with very high mineral matter can land far below “50% CP,” and their AMEn can cluster around the low – to – mid 2,300 kcal/kg range – useful, but not interchangeable with fat – rich animal meals.

AMINO ACIDS, LIMITING AMINO ACIDS, AND DIGESTIBILITY

MBM’s amino acid pattern is often described as “well – balanced” in a general sense, and it can contribute meaningfully to lysine supply. However, for poultry the practical limiting amino acids commonly highlighted are methionine and cystine, and when MBM protein content is elevated (for example, if blood is present), isoleucine can become limiting. 

Digestibility is where MBM separates careful formulators from optimistic ones. Protein digestibility is often reported as high under good processing, but excessive heating reduces digestibility – and this effect is not evenly distributed across amino acids. In large MBM datasets, the digestibility of lysine and sulfur amino acids can span from roughly the mid – 40s up toward the high – 80s (percent), which is a formulation – relevant swing, not an academic footnote. 

CALCIUM, PHOSPHORUS, AND WHAT “AVAILABLE” REALLY MEANS

MBM is frequently used as a non – phytate P source, but modern digestibility work is increasingly cautious about assuming extremely high P availability.

• In broiler assays comparing methods, apparent ileal P digestibility for MBM has been reported around ~42% in one approach, while other calculations (regression – based estimates) yield higher values depending on method and diet design – underscoring that method choice influences the number you believe. 
• Using standardized ileal P digestibility, three MBM sources showed coefficients around 0.49 to 0.69, i.e., substantial variability between batches that were all “MBM.” 

For Ca, published work indicates that Ca concentration and physical characteristics of MBM (including bone – to – soft tissue ratio and particle size distribution) can vary materially across sources, which helps explain why Ca digestibility and Ca – driven interactions differ between mills and regions. 

WHAT PERFORMANCE STUDIES SUGGEST IN BROILERS AND LAYERS

Broilers: growth, feed conversion, and gut-health context.

Broiler performance responses to MBM depend on the inclusion level and whether the diet is balanced on digestible nutrients rather than totals. A classic broiler study using high dietary MBM (up to ~13% high – ash MBM and ~18% low – ash MBM) reported no adverse effects on performance, while warning that adding MBM beyond what is needed for adequate non – phytate P can raise environmental concerns.  More recent work adds an important nuance: MBM can be a valuable P source (reducing the need for inorganic P), but in broilers challenged with subclinical necrotic enteritis, the inclusion of MBM was associated with worse post – challenge growth performance, and the authors interpret part of the mechanism through the lens of undigested protein fermentation and its effects on hindgut environment and Clostridium proliferation. 

From a formulation standpoint, this does not mean “avoid MBM.” It means: if your broiler system is highly constrained on antibiotic use, high – wheat diets, or necrotic enteritis risk, MBM inclusion should be paired with tighter quality specs, digestible amino acid control, and a monitoring plan rather than treated as a drop – In soybean meal replacement. 

LAYERS: EGG PRODUCTION AND SHELL TRAITS

Layer data are often less abundant than broiler data, but a controlled study in older laying hens provides a useful signal: adding 2% MBM improved hen – day egg production, and MBM inclusion improved several eggshell – related traits (e.g., shell ratio and cracked/broken egg rate), though egg weight was depressed and benefits did not scale linearly beyond the lowest inclusion. 

This aligns with what we know about the biology of eggshell formation: sustaining eggshell output requires substantial Ca management, with calcium coming both from intestinal absorption and bone reserves, and shell quality tends to decline as birds age and egg size increases. In that context, a feed ingredient that delivers Ca and P in a concentrated package can plausibly support shell traits – provided the overall Ca supply and particle – size strategy (limestone vs other sources) is rational. 

PHASE – CENTRIC FORMULATION WITH THE LISTED INGREDIENT SET

Our base formula ingredients (corn meal, wheat meal/grain, soybean meal, vegetable oil, limestone, vitamin – mineral premix + salt, and MBM50) are a classic framework for illustrating what MBM50 really does.

• Corn and wheat anchor starch energy but are amino-acid sparse. MBM50 can improve the animal – protein fraction but must be balanced against sulphur amino acids. 
• Soybean meal (44–46% CP) remains the predictable backbone protein, but its P is largely phytate – bound; MBM shifts the P system toward non – phytate mineral P and changes how much limestone you can justify. 
• Vegetable oil becomes more strategic when MBM lots are high ash (lower energy): it can stabilize diet energy without pushing Ca and P higher. 
• Limestone is not “set and forget.” MBM brings Ca at percentage levels, so limestone must be adjusted phase – by – phase – especially in pre – lay and layer diets where Ca targets rise sharply. 

COMPARATIVE PHASE TABLE. The values and inclusion ranges below intentionally mix data – derived nutrient expectations with conservative, phase – appropriate inclusion practice. Where “recommended” inclusion is not universal, I state a plausible range anchored in published layer and broiler usage patterns and extension guidance, and I assume MBM50 is verified by batch analysis.

QUALITY, SAFETY, AND REGULATION

Processing and quality factors that determine “good MBM”.

Rendering is designed to reduce microbial risk, but it is also a nutrient – processing step. Heat treatment, moisture, and particle size influence both pathogen control and nutrient quality; validated processing standards in some trade contexts explicitly specify particle size limits and core thermal conditions (often cited as ~133°C/20 min/3 bar for certain mammalian materials), and industry guidance stresses validation of heat treatments as a control point.  From the nutrition side, the strongest single predictor of “surprise” in MBM is still variability: crude protein, fat, ash, and amino acid digestibility can shift enough between lots to change performance outcomes, which is why routine quality assays and batch – specific formulation are repeatedly recommended in the MBM literature.

BIOLOGICAL HAZARDS, OXIDATION, AND PRACTICAL MITIGATION

A consistent theme across feed safety guidance is that hazards are controlled by GMP/HACCP systems: assess ingredient safety before use, prevent undesirable substances from entering the feed chain, and manage cross-contamination through sanitation and process controls. 

For MBM specifically:

• Salmonella: surveys have detected Salmonella in MBM in some settings (e.g., historical renderery findings and later surveillance), and a modern survey across feed ingredients reported Salmonella presence in a notable fraction of MBM samples. Rendering heat should inactivate Salmonella, but recontamination after cooking (e.g., in handling equipment or moist niches) is a well – recognized problem – meaning your post – process hygiene is as important as your cooker temperature. 

Oxidative rancidity and palatability: because MBM50 often carries meaningful fat, prolonged storage can lead to rancidity and palatability issues unless inventory is rotated and antioxidants are used appropriately; “long – term storage” is therefore a design failure, not a goal.

CHEMICAL CONTAMINANTS AND REGULATORY CONTEXT

On chemical hazards, regulators treat MBM like other feed materials: undesirable substances (e.g., heavy metals, dioxins and related compounds) are controlled through maximum limits and monitoring programs rather than assumptions of safety. European Commission materials summarize that undesirable substances in feed are regulated with maximum permitted levels and that certain practices (e.g., dilution to reach compliance) are not an acceptable substitute for control. 

On BSE/TSE-driven rules, the modern regulatory landscape is nuanced:

• In the European Union, animal by – products are strictly regulated and categorized by risk; EFSA notes that scientific advice informed a 2021 legislative change that partially lifted the feed ban by allowing processed animal proteins from pigs in poultry feed (and vice versa), while maintaining controls intended to prevent intra – species recycling and cross – contamination. 
• In the United States, the regulatory structure is different but likewise rooted in preventing TSE risk: FDA rules prohibit most mammalian protein in ruminant feed and impose labeling/recordkeeping and separation controls, and the “feed ban enhancement” prohibits certain high-risk cattle materials in feed for all species (with implementation guidance emphasizing certification, segregation, and documentation).