Meat by-products in cat food are the parts of slaughtered animals that aren’t skeletal muscle meat. This includes organs like liver, kidneys, lungs, spleen, and brain, along with blood, bone, and intestines. Despite their unappetizing reputation, many of these parts are nutrient-dense and reflect what cats would naturally consume when eating prey in the wild.
The Official Definition
The Association of American Feed Control Officials (AAFCO), which sets ingredient standards for pet food in the U.S., defines meat by-products as “the non-rendered, clean parts, other than meat, derived from slaughtered mammals.” The definition specifically lists lungs, spleen, kidneys, brain, liver, blood, bone, partially defatted fatty tissue, and stomachs and intestines freed of their contents.
Equally important is what the definition excludes. Hair, horns, teeth, and hooves are not allowed in meat by-products. The ingredient must also be “suitable for use in animal food,” which means it has to meet basic safety and quality standards before it goes into your cat’s bowl.
Meat By-Products vs. Poultry By-Products
“Meat by-products” refers specifically to mammals, typically cattle, pigs, sheep, or goats. When the source is a bird, the label will say “poultry by-products” or “poultry by-product meal” instead. Poultry by-products include feet, necks, undeveloped eggs, intestines, and sometimes beaks. This is distinct from “chicken meal,” which is made primarily from the skin, flesh, and bones of processed birds.
The word “meal” on a label means the ingredient has already been rendered, a process that removes moisture and fat through sustained heat. A “by-product meal” is the dried, ground version of by-products, while plain “by-products” are used in their fresh, wet form, typically in canned foods.
How By-Products Are Processed
When by-products are turned into a meal for dry cat food, they go through rendering. The raw material is ground into a uniform size, then cooked with steam at temperatures between 240°F and 290°F for 40 to 90 minutes. This step kills bacteria, viruses, parasites, and other pathogens. After cooking, the fat is pressed out, and the remaining protein-rich material is dried and ground into the powder that gets mixed into kibble. The entire process is monitored with computer-controlled time and temperature tracking to ensure safety.
For wet cat food, fresh by-products skip the rendering step and are cooked directly during the canning process, which also sterilizes the final product.
Nutritional Value for Cats
By-products have a bad reputation largely because of how they sound, not because of how they perform nutritionally. Organ meats are some of the most nutrient-dense foods a cat can eat. Liver provides high levels of vitamin A, vitamin K, iron, and phosphorus. Kidneys supply vitamin A, vitamin C, vitamin D, calcium, iron, and phosphorus. Compared to plain skeletal muscle, organs deliver a broader range of vitamins and minerals in concentrated amounts.
Cats are obligate carnivores, and in the wild they eat nearly every part of their prey, organs included. A diet of nothing but lean muscle meat would actually leave a cat deficient in several essential nutrients. Research on cat diets containing poultry by-product meal has found digestibility rates around 90% for protein and gross energy, which is comparable to diets made with whole muscle ingredients. In practical terms, cats absorb and use the nutrients from well-processed by-products efficiently.
What “Named” vs. “Unnamed” Sources Mean
One of the most useful things you can look for on a cat food label is whether the by-product names its animal source. “Chicken by-products” or “beef by-products” tell you exactly which species went into the food. A generic label like “meat by-products” or “animal by-products” does not specify the source, which means the supplier can use whatever mammals are available at the time of production. This makes it harder to know what your cat is eating, and it’s a particular problem if your cat has a food sensitivity or allergy to a specific protein.
Named by-products also tend to signal a manufacturer that exercises more control over its ingredient sourcing. If a company is willing to lock in a specific protein source, it generally means they have a more consistent supply chain. When comparing two cat foods that both contain by-products, the one that names the species is giving you more transparency.
How to Evaluate By-Products on a Label
By-products aren’t inherently bad, but their quality can vary. Here’s what to consider when you see them on a label:
- Position on the ingredient list. Ingredients are listed by weight. A by-product listed first or second contributes significantly to the food’s protein content. One listed near the end is a minor component.
- Named vs. unnamed source. “Chicken by-products” is more informative than “meat by-products.” If your cat has dietary sensitivities, named sources let you control what proteins they’re exposed to.
- Meal vs. fresh. “Poultry by-product meal” is a concentrated protein source because the water has been removed. Fresh “chicken by-products” in a canned food contain more moisture, so the actual protein contribution per pound is lower.
- What else is in the food. A cat food with named by-products alongside whole meats, added taurine, and minimal fillers can be a perfectly balanced diet. By-products become more of a concern when they’re the sole protein in a food loaded with plant-based fillers and vague ingredients.
Many veterinary and premium cat foods use by-products intentionally because of their organ meat content. The presence of by-products alone doesn’t make a food low quality, just as their absence doesn’t automatically make a food superior. What matters is the overall formulation, whether the food meets AAFCO nutritional profiles, and how your individual cat does on it.