Are by-products and animal meals bad? An evidence guide
Are by-products and animal: Few words trigger more distrust on a pet food label than "by-product". It sounds like a leftover, something swept off the floor of a slaughterhouse. Yet the regulatory and nutritional record tells a very different story. An animal by-product is simply a part of the carcass other than skeletal muscle: liver, kidney, heart, lung, spleen. In the European Union, only Category 3 material, judged fit for human consumption at slaughter, may enter animal feed at all (Regulation (EC) 1069/2009). The real question is never the term but the transparency of the label behind it.
Last updated :General documentary information. For an individual animal, a veterinarian's advice takes precedence over any online content.
This guide weighs the common belief against the evidence, keeps EU and US status distinct, and gives the level of confidence for each claim. It covers by-products, animal meals, offal, crude ash and the supply-chain logic that explains why a perfectly good organ ends up with an unappetising name.
On this page
- What does the law actually let into the bowl?
- Is offal really nutritionally poor?
- Are animal meals a lower grade of protein?
- Why do some labels say "meat and animal by-products" with no species?
- Does a high crude ash figure mean too much bone or by-product?
- How does Category 3 differ from material unfit for feed?
- Comparison: how the label wording maps to real quality
- The verdict: judge the source, not the word
What does the law actually let into the bowl?
Answer capsule. A by-product is any edible part of a slaughtered animal that is not skeletal muscle. In the EU, Regulation (EC) 1069/2009 sorts animal material into three risk categories and admits only Category 3, the lowest risk, into animal feed; Categories 1 and 2 are banned outright (Regulation (EC) 1069/2009). No legal text anywhere equates the word with waste.
Category 3 covers animals declared fit for human consumption at the point of slaughter but diverted from the human chain for commercial reasons. The control therefore happens upstream, at the abattoir, under veterinary inspection, long before the material reaches a kibble line. That is why a pack never states a "category": the law presumes that any by-product present is Category 3, because nothing else is permitted (Regulation (EC) 767/2009). The absence of the word is the consequence of a prohibition, not a gap.
In the United States, AAFCO publishes named definitions such as "poultry by-product" that exclude feathers, beaks, teeth, horns and hooves beyond set thresholds. Both frameworks bound the material tightly rather than leaving it open. The level of evidence here is documentary and regulatory: it follows directly from EU texts and published AAFCO definitions, not from interpretation.
Is offal really nutritionally poor?
Answer capsule. No. Offal (US: organ meat) ranks among the most nutrient-dense components of a ration. Liver concentrates vitamin A, haem iron, copper, zinc and B vitamins above the levels in lean muscle; heart supplies taurine, essential for the cat; gizzard delivers lean protein (FEDIAF, 2024; NRC, 2006). The WSAVA notes that organs belong to the natural diet of carnivores.
A surprising detail makes the point: in a prey carcass, organs supply a share of micronutrients far larger than their relative weight. These tissues are so concentrated that excess matters more than scarcity. Too much liver can cause vitamin A toxicity, or hypervitaminosis A, a risk documented by the NRC (NRC, 2006). An ingredient that has to be dosed carefully because it is so rich is the opposite of a filler.
The evidence on the nutritional value of Category 3 offal is high, resting on long-standing, reproducible composition data. The distrust is cultural: it springs from the connotation of the word "by-product", not from any measured deficiency. The single legitimate caveat is variability. A named entry, such as chicken liver, tells more than a vague one. That is a traceability argument, not a toxicity one.
Are animal meals a lower grade of protein?
Answer capsule. No, not as a rule. An animal meal results from a cooking and drying process (rendering) that removes water and part of the fat, leaving a stable powder rich in protein. Weight for weight, a meal supplies more protein than fresh meat, which is roughly 70 percent water (Tufts Petfoodology). The word "meal" describes concentration, not inferior quality.
This has a practical consequence many owners miss. Because ingredients are ranked by pre-cooking weight, fresh meat sits high on the list but loses most of that weight on drying, while a meal can sit lower yet contribute more protein to the finished product (AAFCO; Tufts Petfoodology). A food that proudly lists fresh meat first may, after extrusion, draw the bulk of its protein from a less visible meal.
The real quality issue is not the category but the precision of the name. "Chicken meal" identifies a source and is governed by AAFCO and FEDIAF; a generic "meat meal" with no species stated may mix heterogeneous origins from batch to batch, which weakens traceability (FEDIAF, 2024). The evidence on protein density is high and measurable by composition analysis; the variability of a generic meal is a matter of traceability, not demonstrated toxicity. With equal information, a named meal is the better signal.
Why do some labels say "meat and animal by-products" with no species?
Answer capsule. Because the law allows it. Regulation (EC) 767/2009 permits ingredient-category designations such as "meat and animal by-products" or "cereals" without naming the species. This gives the manufacturer sourcing flexibility and lets recipes flex with raw-material prices, but it reduces transparency for the buyer.
The cost of that flexibility falls hardest on owners managing a food allergy. A reliable elimination diet requires knowing every protein the animal ingests, and a group designation can switch source species from batch to batch while staying fully compliant (WSAVA). For a dog sensitive to chicken, a category label makes the elimination impossible to verify. In that situation a named statement stops being a matter of trust and becomes a safety criterion.
This is where compliance and transparency part company. A maker can stay within the law while remaining vague, which is exactly why two equally legal labels can inform so unequally. Regulatory compliance secures the baseline; precision on the label is the maker's choice. The evidence is regulatory on the allowance and methodological on the allergy stake.
Does a high crude ash figure mean too much bone or by-product?
Answer capsule. Not directly. Crude ash is not an added ingredient but an analytical measurement: the non-combustible mineral residue left after laboratory calcination, reflecting mostly calcium, phosphorus and magnesium (FEDIAF, 2024). A level around 5 to 8 percent on a dry-matter basis is common and expected in a balanced complete food.
A markedly higher figure may point to a large bone or mineral fraction, which raises a calcium-to-phosphorus balance question rather than a by-product one (NRC, 2006). The point to watch is the ratio, not the raw number, and it matters most during growth: in a large-breed puppy a calcium and phosphorus imbalance is more concerning than the ash figure itself. A surprising flip is worth keeping in mind: too low an ash level can signal a mineral shortfall just as readily as a high level prompts scrutiny.
The evidence on what ash measures is high and consensual. The figure is always read relative to dry matter and life stage, never in isolation, which is the same disciplined reading the rest of this guide applies to by-products and meals.
How does Category 3 differ from material unfit for feed?
Answer capsule. Category 3 comes from inspected animals judged fit for human consumption at slaughter, and it alone enters animal feed. Categories 1 and 2, covering specified risk material and animals dead outside the chain, are unfit and banned (Regulation (EC) 1069/2009). The difference is one of health status and traceability, decided at the abattoir, not a question of vocabulary.
The classification rests on the health risk of the material, not its appearance. Category 3 gathers parts of slaughtered, inspected animals diverted from the human chain for commercial reasons; Categories 1 and 2 are strictly excluded from feed. This is why a finished pack never states a category: the law presumes that any by-product present must be Category 3, since nothing else is permitted (Regulation (EC) 767/2009). The absence of the word on a bag is the consequence of an upstream prohibition, not a gap in the labelling.
That upstream control is the point most easily missed. The buyer does not see the health sorting because it has already taken place under veterinary inspection before the material ever reached the recipe. The finished product inherits a control performed at slaughter. The evidence on the three-category sorting is high and traceable, resting on harmonised inspection rather than a visual judgement of the finished food.
Comparison: how label wording maps to real quality
The table below sets the common designations side by side on the criteria that actually matter: traceability, nutritional contribution and regulatory footing. Note that none of these wordings is a danger signal on its own; they differ in how much they tell you.
| Label wording | EU regulatory status | Protein or nutrient value | Traceability | Quality signal |
|---|---|---|---|---|
| Named by-product (e.g. chicken liver) | Permitted, Category 3 (Reg. (EC) 1069/2009) | High (vitamin A, iron, taurine) | Good | Strong, names organ and species |
| Named meal (e.g. chicken meal) | Governed (AAFCO, FEDIAF) | High and stable | Good | Strong, process plus source |
| Generic meal (no species) | Permitted | High but variable | Weak | Needs more detail |
| "Meat and animal by-products" | Permitted (Reg. (EC) 767/2009) | Variable by batch | Weak | Low, hinders allergy management |
| Fresh meat listed first | Permitted | Falls sharply after drying | Good if species named | Weaker than it looks |
The verdict: judge the source, not the word
The evidence points one way. By-products and animal meals are neither dangerous nor low grade by definition. EU law admits only inspected, human-grade Category 3 material into feed (Regulation (EC) 1069/2009), offal is among the densest sources of vitamin A, iron and taurine in a ration (FEDIAF, 2024; NRC, 2006), and a meal is simply a concentrated, dehydrated protein (Tufts Petfoodology). The genuine weakness is opacity, not toxicity.
The practical recommendation follows directly. Favour a label that names the organ or the species (chicken liver, lamb meal) over a group designation such as "meat and animal by-products", above all if your animal has a suspected food allergy. Read the guaranteed average analysis and the "complete and balanced" statement for the life stage rather than ranking ingredients by their position on the list. And treat the word "by-product" itself as a neutral supply-chain term, not a verdict. Where a maker stays vague, a direct question about the source is the most reliable next step.
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Keep reading
Related questions: Are animal by-products dangerous for a dog or cat? | Are by-products and animal meals necessarily low quality? | Is a meat meal more concentrated in protein than fresh meat?
Glossary: Meat and animal by-products | Crude ash (ash content)
Hub: Controversial ingredients: myths versus evidence
Sources: Regulation (EC) 1069/2009 and Regulation (EC) 767/2009 (EUR-Lex); FEDIAF Nutritional Guidelines 2024; NRC, Nutrient Requirements of Dogs and Cats (2006); WSAVA Global Nutrition Guidelines; AAFCO, Understanding Pet Food; Tufts Petfoodology (Cummings Veterinary Medical Center).