Meat and bone meal (MBM) is a dry, powdered product made by cooking down and grinding animal byproducts from slaughterhouses, including bones, organs, and trimmings that aren’t sold as meat for human consumption. It contains roughly 50 to 55% protein along with high concentrations of calcium and phosphorus, making it a widely used ingredient in animal feed, pet food, and garden fertilizers.
How Meat and Bone Meal Is Made
The production process is called rendering. Slaughterhouse byproducts are heated to high temperatures to kill bacteria, remove moisture, and separate fat from solids. The remaining material is then ground into a fine, brownish powder. The process excludes blood, hair, hooves, horns, hide trimmings, and stomach contents, though trace amounts of these may be present from normal processing.
The raw materials come from mammal tissues only. Poultry byproduct meal and fish meal are separate products with their own definitions and nutritional profiles. When a label says “meat and bone meal” without further description, it typically comes from cattle, pigs, or sheep.
Nutritional Profile
MBM packs a lot of protein and minerals into a small volume. The protein content runs between 50 and 55%, though the amino acids in that protein are harder for animals to digest compared to whole meat or soybean meal. One amino acid in particular, tryptophan, is present in very low amounts, which means nutritionists need to account for that gap when formulating diets.
Where MBM really stands out is its mineral content. It must contain at least 4% phosphorus, and calcium levels cannot exceed 2.2 times the phosphorus level. Phosphorus from MBM has relatively high bioavailability, meaning animals can absorb and use a good portion of it. This makes it a cost-effective alternative to supplemental mineral sources in livestock and poultry diets.
Quality is measured partly by digestibility. Under AAFCO (Association of American Feed Control Officials) standards, MBM cannot contain more than 12% pepsin indigestible residue, which is the portion left over after simulating stomach digestion in a lab. No more than 9% of the crude protein can be indigestible by the same test. Products that fail these thresholds contain too much connective tissue or low-quality material to be useful as feed.
Uses in Animal Feed
MBM is fed to poultry, pigs, and farmed fish as a protein and mineral supplement. In broiler chicken diets, for example, inclusion rates typically start around 10% in starter feeds for young chicks and drop to about 5% in finishing diets as the birds approach market weight. The exact percentage depends on the nutritional quality of the specific MBM batch, since composition can vary between rendering plants and even between production runs at the same facility.
Nutritional variability is one of the biggest practical challenges with MBM. Unlike soybean meal, which has a fairly predictable protein and amino acid profile, MBM can shift significantly in quality depending on the mix of raw materials that went into a particular batch. Livestock nutritionists routinely test MBM samples and adjust formulas accordingly.
MBM in Pet Food
You’ll find meat and bone meal listed on many dog and cat food labels. AAFCO requires that it appear by its specific ingredient name, not hidden under vague umbrella terms like “animal protein products.” All ingredients on pet food packaging must be listed individually in descending order by weight, so where MBM falls on the list tells you roughly how much of the product it makes up.
If the MBM comes from a specific animal, the label should say so, such as “beef and bone meal” or “pork and bone meal.” A generic “meat and bone meal” listing means it could come from any combination of approved mammal sources. This distinction matters if your pet has a known protein sensitivity or allergy.
Use as a Garden Fertilizer
Outside of animal feed, MBM is sold as an organic fertilizer. Bone meal fertilizer has a typical N-P-K ratio of about 4-12-0, meaning it’s very high in phosphorus relative to nitrogen and contains essentially no potassium. Steamed bone meal runs closer to 1-13-0. This makes it particularly useful for promoting root development and flower production in plants that need a phosphorus boost, though you’ll need a separate source for nitrogen and potassium.
Because MBM breaks down slowly in soil, it releases nutrients over weeks rather than all at once. Gardeners commonly work it into the soil at planting time for bulbs, roses, and root vegetables.
Safety Regulations and BSE
The most significant safety concern around MBM involves bovine spongiform encephalopathy (BSE), commonly known as mad cow disease. The infectious proteins that cause BSE can survive rendering temperatures, which means feeding MBM from infected cattle back to other cattle creates a transmission cycle.
In 1997, the FDA banned feeding mammalian protein, including MBM, to cattle and other ruminant animals (sheep, goats, deer). This rule remains in effect. A 2008 enhancement went further, prohibiting certain high-risk cattle materials from entering feed for any animal species. These banned materials include brains and spinal cords from cattle 30 months of age and older, the entire carcasses of BSE-positive cattle, and the carcasses of cattle that weren’t inspected and passed for human consumption (unless the animal was under 30 months old or the brain and spinal cord were removed). Even tallow, the rendered fat, must contain no more than 0.15% insoluble impurities if it’s going into ruminant feed.
These regulations mean MBM produced today in the United States is used primarily in poultry, swine, aquaculture, and pet food, not in cattle feed.
Environmental Impact of Rendering
Rendering serves an important environmental function by keeping millions of tons of slaughterhouse waste out of landfills each year. An average rendering plant sequesters about five times more greenhouse gas emissions than it produces, largely because the alternative, landfilling or composting that same organic material, would release far more methane and carbon dioxide. By one estimate, rendering avoids at least 90% of potential greenhouse gas emissions compared to industrial composting, equivalent to removing 18.5 million cars from the road annually.
Rendered animal fat also finds use as a biofuel feedstock. Fuel produced from rendered fat generates about 20.7 grams of CO2 equivalent per megajoule of energy, compared to 94.4 grams for conventional diesel. That roughly 78% reduction in carbon intensity is one reason the rendering industry has become increasingly tied to renewable fuel markets.