Meat By-Products in dog and cat food

Is it OK for dogs and cats?

Dogs

Meat by-products are a permitted protein source in US dog food, and AAFCO's position is that by-products can be used safely to provide nutrition. Quality depends on which parts are used: in chick and rooster tests, most freeze-dried raw materials, including lung and liver, showed moderate to high protein quality.

Cats

AAFCO's position on by-products is not limited to dogs, but the protein-quality study cited here did not test cats. Cats need taurine, arachidonic acid and vitamin A from their diet, so whether a cat food covers these depends on the whole recipe, not on one ingredient.

How settled this is: A popular concern the sources do not support

What meat by-products is

AAFCO's consumer guide describes meat by-products as the clean parts of slaughtered mammals, other than meat, that have not been rendered. They include organs and bone but not hair, horns, teeth or hooves. 'Meat' itself means mainly muscle tissue, including heart and diaphragm muscle, with the fat and gristle that normally come with it. The species must be named unless the animals are cattle, pigs, sheep or goats. US rules require ingredients to be listed by their common or usual name, heaviest first. FDA says names defined by AAFCO may serve as those common names.

Why it is in pet food

Slaughter produces internal organs and other parts that are not normally used for human food, and AAFCO notes that such parts can be expected to go into animal feed. AAFCO also notes that some by-products, such as liver, kidney and tripe, are eaten by some people. AAFCO's position is that by-products are not unsafe or lacking in nutrition simply because they are not the main product.

What it does in the food

Meat by-products supply animal protein, and protein quality varies with the parts used. One study tested six freeze-dried raw materials, including beef, pork and sheep lungs and pork liver, in chicks and roosters. Most of the raw materials showed moderate to high protein quality, and pork liver scored highest overall. The rendered meals in the same study (lamb meal and poultry by-product meals) generally scored lower (Cramer et al., 2007). Plant proteins contain no taurine, so cats need some animal-based protein or added taurine (Merck Veterinary Manual).

Safety and limits

AAFCO's position is that by-products can be used safely to provide nutrition. Raw by-products may carry bacteria such as Salmonella or E. coli, so they must be heat-treated before use in finished feed. Commercial canned and dry pet foods are heat-treated during manufacture. AAFCO's consumer guide also says that meat and by-products from animals that died other than by slaughter are considered adulterated. Such material cannot be used in feed unless it contains no chemical additives and is heat-treated and further processed. For cattle, US rules bar certain materials from the food or feed of all animals to reduce the risk of BSE. These include the brains and spinal cords of cattle aged 30 months or older (21 CFR 589.2001).

What depends on the amount and the recipe

Which parts and species are used. How the raw material is handled and cooked. How the full recipe is balanced. For cats, the complete food must also meet cat-specific needs such as taurine.

Not the same as

• Meat — Mainly muscle tissue with the fat and gristle that normally come with it. By-products are the other parts.
• Meat meal — Mammal tissue that has been rendered (cooked, dried and ground). Meat by-products are not rendered.
• Meat and bone meal — A rendered dry meal made from mammal tissue that includes bone.
• Poultry by-products / poultry by-product meal — Come from birds, not mammals.

Sources

1. What's in the Ingredients List? (ingredient definitions explained for consumers) — Association of American Feed Control Officials (AAFCO). Definitions of meat by-products (non-rendered, organs and bone, no hair, horns, teeth or hooves; some, such as liver, kidney and tripe, are eaten by people), meat (primarily muscle tissue, including heart and diaphragm), meat meal and meat and bone meal. Species must be named unless cattle, pigs, sheep or goats.
2. Byproducts (Understanding Pet Food) — Association of American Feed Control Officials (AAFCO). AAFCO's position that by-products can be used safely to provide nutrition. Organs not used for human food may go into feed. Raw by-products may carry Salmonella or E. coli and must be heat-treated. Material from animals that died other than by slaughter counts as adulterated unless it meets the stated conditions.
3. Animal Food Labeling and Pet Food Claims — U.S. Food and Drug Administration, Center for Veterinary Medicine, 2026. Ingredients must be listed by common or usual name in descending order by weight (21 CFR 501.4(a)). AAFCO-defined names may be common usage names.
4. Cramer KR et al. Protein quality of various raw and rendered by-product meals commonly incorporated into companion animal diets. J Anim Sci 85(12):3285-3293 — Journal of Animal Science, 2007. In chick and rooster assays, most of six freeze-dried raw meals (including beef, pork and sheep lungs and pork liver) showed moderate to high protein quality, with pork liver highest overall. The rendered meals tested (lamb meal and poultry by-product meals) generally had lower protein quality.
5. 21 CFR 589.2001 Cattle materials prohibited in animal food or feed to prevent the transmission of bovine spongiform encephalopathy — U.S. Electronic Code of Federal Regulations (eCFR), 2019. Bars certain cattle materials, including brains and spinal cords of cattle 30 months of age and older, from the food or feed of all animals.
6. Nutritional Requirements of Small Animals — Merck Veterinary Manual, 2024. Unlike dogs, cats need dietary vitamin A, arachidonic acid and taurine. Plant proteins contain no taurine, so cats need some animal-based protein or added taurine.

Checked against these sources on 2026-10-15. Definitions are in our own words. This is a reading aid, not veterinary advice: a vet who knows your animal comes first.