What Are By-Products in Dog Food? Myth vs the Real Definition

The AAFCO definition: what's actually in “meat by-products”

AAFCO — the regulatory body that writes the model definitions for pet food ingredients — defines meat byproducts as “the non-rendered, clean parts, other than meat, derived from slaughtered mammals,” and lists the specific contents: “lungs, spleen, kidneys, brain, livers, blood, bone, partially de-fatted low temperature fatty tissue and stomachs and intestines freed of their contents.” (see AAFCO ▼)

In plain English, that's organ meats (liver, kidneys, lungs, spleen, brain), blood, bone, fatty tissue, and emptied stomachs and intestines. These are the parts of an animal that humans in Western diets typically don't eat — not because they're unsafe, but because cultural preference favours skeletal muscle.

AAFCO makes that human-vs-animal distinction explicit: “Although the USDA does not deem certain byproducts, such as udders and lungs, edible for human consumption, they can be perfectly safe and nutritious for other animals.” (see AAFCO ▼)

What's NOT in meat by-products

The AAFCO definition closes with an explicit exclusion list. Meat byproducts does not include:

• Hair
• Horns
• Teeth
• Hoofs

That's the regulatory definition — verbatim. (see AAFCO ▼) When a regulator says “A is defined as X, NOT including Y,” that's an operational, audited definition — not a marketing claim that might or might not be true.

AKC's nutrition writers give a parallel framing of what regulated byproducts exclude: “Regulated byproducts don't include hooves, hair, floor sweepings, intestinal contents, or manure.” (see AKC ▼) Same point, slightly broader list — the things most people picture as “garbage” aren't in the regulatory definition at all.

Poultry by-products vs meat by-products

AAFCO defines “meat byproducts” and “poultry byproducts” separately because they come from different animals. Meat byproducts come from mammals (cattle, pigs, lambs). Poultry byproducts come from birds (chicken, turkey, duck).

The AAFCO definition of poultry byproducts: “Non-rendered clean parts of carcasses of slaughtered poultry, such as heads, feet and viscera, free from fecal content and foreign matter except in such trace amounts as might occur unavoidably in good factory practice.” (see AAFCO ▼)

Two things to notice. First, poultry byproducts include parts (heads, feet) that aren't in the mammalian definition — because birds are processed differently than mammals. Second, the regulatory wording is explicit about being “free from fecal content,” which addresses another common misconception directly.

What does “by-product meal” mean?

The word “meal” on a pet-food ingredient label means the ingredient has been rendered: cooked, with water and most fat removed, leaving a concentrated dry powder. AKC's veterinary author explains the concept for chicken meal: “Chicken meal means chicken with the water and fat removed. It weighs less than chicken but actually can contain a higher percentage of protein.” (see AKC ▼) The same logic applies to byproduct meals: take the fresh byproduct ingredient, render it, and you get a concentrated protein-and-mineral powder.

AAFCO has its own regulatory definition for the poultry side: “Poultry By-Product Meal: Consist of the ground, rendered, clean parts of the carcass of slaughtered poultry, such as necks, feet, undeveloped eggs and intestines, exclusive of feathers except in such amounts as might occur unavoidably in good processing practices.” (see AAFCO ▼)

So “byproducts” on a label is the fresh form; “byproduct meal” is the same underlying material with water removed, often delivering more protein per gram than the fresh equivalent. The “meal” suffix is a processing step, not a downgrade.

Are by-products bad for dogs?

The short answer is no — not by virtue of being called a byproduct. AKC's Jan Reisen puts it plainly: “While we may not want to eat them, byproducts aren't necessarily a bad addition in dog food. They include parts such as the liver, which is rich in vitamin A. Other byproducts include blood, brains, bone, stomach, and cleaned intestines.” (see AKC ▼)

Three things by-products are not:

• Garbage or waste. The regulatory exclusion list (see the previous section) covers what people imagine as garbage — hair, horns, teeth, hoofs, floor sweepings, manure. None of those are in the definition. What IS in the definition (organs, blood, bone, fatty tissue) is operationally audited.
• Low-quality protein. Organ meats are often more nutritionally dense than skeletal muscle. AKC: “Quality animal byproducts are also nutritious. These include organ meats and entrails, which often contain more nutrients than the muscle meat consumed by humans.” (see AKC ▼)
• Inferior to fresh “chicken” or “beef” on the ingredient list. Those whole-meat terms include water weight; after kibble drying the named whole meat can deliver less protein per gram than a meal form. Form factor and concentration matter — not just whether the ingredient name has the word “byproduct” in it. (For the water-weight mechanic, see our label-reader hub.)

AAFCO directly addresses the human-vs-animal framing too: “Although the USDA does not deem certain byproducts, such as udders and lungs, edible for human consumption, they can be perfectly safe and nutritious for other animals.” (see AAFCO ▼) Human-inedible doesn't mean animal-inedible — that equation is a marketing frame, not a regulatory one.

What matters for picking a food is the full Guaranteed Analysis, the AAFCO Nutritional Adequacy Statement, and your dog's actual response — not whether the ingredient name contains the word “byproduct.”