The Word That Makes Dog Owners Nervous
Few terms in pet food cause more unease than "by-product." It sits in ingredient lists looking vaguely threatening, and a significant portion of pet food marketing has been built around the promise of being "by-product free." The reality, however, is considerably more complicated than the marketing suggests, and understanding what by-products actually are requires setting aside a few common assumptions.
The short version is this: by-products are not inherently poor-quality ingredients, and some of them are genuinely nutritious. The longer version involves understanding what the term means technically, why context matters, and what the actual quality concerns are in the by-product conversation.
What AAFCO Actually Defines as a By-Product
AAFCO provides specific definitions for common pet food ingredients. Poultry by-products, for example, are defined as the non-rendered, clean parts of slaughtered poultry other than meat. This includes organs such as the heart, liver, and kidneys, as well as the neck, feet, and undeveloped eggs. Feathers are not included unless they appear in a separately listed ingredient.
Poultry by-product meal involves the same parts but rendered, meaning the material has been cooked under high heat and pressure to remove water and fat, leaving a concentrated protein-rich powder. By that definition, a chicken liver is a by-product. So is a gizzard. Both are organs that have been consumed by humans across many cultures for centuries and are considered nutrient-dense foods.
The aversion to by-products in pet food is largely a Western cultural phenomenon rooted in the fact that organ meats have fallen out of favour in mainstream human diets. In nutritional terms, many of those organs are actually more micronutrient-dense than muscle meat.
The Nutritional Case for Organ Ingredients
Liver, in particular, is one of the most nutritionally concentrated animal-source ingredients available. It is rich in vitamin A, B vitamins including B12 and folate, iron, zinc, and copper. Heart muscle is an excellent source of taurine and CoQ10. Kidneys provide high-quality protein alongside a range of B vitamins.
In the context of a prey-model or species-appropriate diet, organ meats are considered essential components, not filler. Dogs in the wild consume the whole animal, and the organs are typically among the first parts eaten. Framing these ingredients as inferior to muscle meat misrepresents their actual nutritional contribution.
This does not mean that all by-products are equivalent. Quality varies significantly, which brings us to the parts of the by-product conversation that actually deserve scrutiny.
Where Legitimate Concerns Exist
The genuine concern with by-products is not that they are organs. It is the vagueness of what can fall under the term in lower-grade products, and the variability in sourcing and quality control.
In the US, AAFCO definitions for by-products exclude hair, horns, hooves, hide trimmings, manure, and stomach contents. However, enforcement and auditing standards vary, and not all manufacturers operate under the same level of scrutiny. Some lower-grade by-product meals have historically included ingredients of questionable nutritional value or sourcing.
Another issue is specificity. An ingredient listed simply as "poultry by-product meal" does not tell you which birds it came from or in what proportions. A named by-product, such as "chicken by-product meal," is preferable because it identifies the species and implies a level of consistency. Unnamed or generic by-product meals allow more variability in composition across batches.
The Difference Between Meal and Fresh By-Products
It is worth understanding the distinction between fresh by-products and by-product meal, as they behave quite differently in a formulation.
Fresh by-products are listed on an as-fed basis, which means their weight includes a high proportion of water, typically 70 to 80 percent. After cooking, the actual dry matter contribution is substantially smaller. A food that lists "chicken by-products" high in the ingredient list may contain less actual chicken by-product than you might expect once moisture is accounted for.
By-product meal has already had water removed during rendering, meaning it is a concentrated protein source. A food listing "chicken by-product meal" earlier in the ingredient list is likely delivering a more meaningful contribution of that ingredient to the finished product. Neither format is inherently better or worse, but understanding the water content difference helps you read the ingredient list more accurately.
How to Evaluate By-Products on a Label
Rather than avoiding all by-products categorically, a more useful approach involves asking specific questions about how they appear on a label:
- Is the species named? "Chicken by-product meal" is more informative than "poultry by-product meal."
- Which specific organs or parts are included, if the brand discloses this information?
- Is the manufacturer transparent about their sourcing and quality standards?
- Does the overall guaranteed analysis support the nutritional profile you are looking for?
A food from a transparent manufacturer that uses named by-product meals alongside other quality ingredients may well outperform a "by-product-free" food built primarily on plant proteins and unnamed meat meals. The label claim tells you less than the full picture of the formulation.
The Marketing vs. Nutrition Gap
Pet food marketing has done an effective job of equating "no by-products" with quality. In some cases this reflects a genuine commitment to identifiable, named ingredients. In other cases it is primarily a positioning strategy, and the absence of by-products does not guarantee superior nutrition.
A food can exclude by-products entirely and still contain low-quality protein sources, excessive carbohydrate fillers, or an unbalanced mineral profile. Meanwhile, a food containing clearly identified organ meats from reputable suppliers can offer excellent digestibility and micronutrient density.
The goal as a dog owner is not to find a label that says the right things, but to understand what is actually in the bag and whether it meets your dog's nutritional needs. By-products, evaluated on their own merits rather than the surrounding cultural assumptions, are a nuanced part of that picture rather than a straightforward red flag.