What the AAFCO Definitions Actually Say
Under AAFCO definitions, by-products are the clean, non-rendered parts of a slaughtered animal other than skeletal muscle: liver, kidneys, heart, spleen, lungs, blood, and bone. Feathers, hair, horns, teeth, hooves, and stomach or intestinal contents are explicitly excluded. “Meal” refers to the rendered, dried versions: poultry by-product meal is the ground, rendered product from those same clean parts.
Meal also applies to muscle meat. Chicken meal is chicken with most of its water and fat removed, and it may not contain added blood, hair, hide trimmings, manure, or stomach contents. In amino acid terms, veterinary nutritionists treat a named meal as equivalent to its fresh counterpart — just concentrated.
The Moisture Math Behind Ingredient Lists
Ingredient lists are ordered by weight, water included. Fresh chicken is roughly 70 percent moisture; chicken meal is around 10 percent. That is why “fresh chicken first” headlines are so easy to engineer: a manufacturer can weigh wet ingredients ahead of the dry ones that actually deliver more protein. A food that opens with fresh meat followed by a named meal is often more protein-dense than its label implies. The point is not that fresh meat is bad — it is that the list rewards wet weight, not nutrition.
- “Chicken” — wet weight, about 70 percent water
- “Chicken meal” — concentrated, roughly three times the protein by weight
- “Chicken by-product meal” — rendered organ and carcass parts of one named species
- “Meat by-product meal” or “animal by-product” — unnamed species, variable composition
Why Organ Meats Are Not Waste
The “by-products are floor sweepings” story collapses on nutritional facts. Liver is one of the most nutrient-dense foods that exists, packed with vitamin A, iron, copper, and B vitamins. Heart supplies taurine and lean protein; kidney and spleen round out the amino acid profile. Many veterinary therapeutic diets — the foods prescribed for kidney disease and bladder stones — contain named by-products precisely because they are digestible and nutrient-dense.
WSAVA’s manufacturer-selection guidelines never list “no by-products” as a quality criterion; they focus on whether a company employs qualified nutritionists, runs feeding trials, and controls quality. The stigma is largely a Western marketing phenomenon that took off in the early 2010s, when “no by-products” became a premium price tag rather than a nutritional argument.
Named Beats Generic Every Time
Quality does vary — just not the way most owners assume. “Chicken by-product meal” identifies the species, which brings traceability and batch-to-batch consistency. A generic “meat by-product” could be almost any mammal, which makes it harder to manage food sensitivities or judge quality. Prefer foods that name the animal: the species name, not the word “by-product,” is the signal worth reading on the list.
It also helps to remember what the alternatives often are. Foods that advertise “no by-products” usually replace those organ meats with plant protein concentrates or additional carbohydrate sources, then add back the missing vitamins and minerals as synthetic supplements. That is not unsafe — but it means the “cleaner” label can describe a less biologically appropriate mix of ingredients, not a better diet. Reputable manufacturers that use by-products typically source them from food-grade slaughterhouses, and many premium brands state exactly which organs they include.
If your pet thrives on a food containing by-product meal, there is no nutritional reason to switch. Judge the manufacturer — its nutrition staff, its quality control, its feeding trials — rather than a single ingredient word chosen to scare you.