How To Evaluate Dog Food Protein

dog food protein

Dogs are carnivores. While they are technically “facultative omnivores” who can derive nutrition from a wide variety of foods, prey animals are their natural diet. Prey contain muscle meat, organs and glands, skin and connective tissue, and bones. But whole, fresh prey are not readily available. So pet food makers have stepped in with a vast array of products designed to provide the individual nutrients in the prey diet.

Here’s what you need to know about how to evaluate dog food protein.

What Is Protein?

Protein is the big divide among foods in terms of nutritional value. 

Proteins are made of chains of amino acids. Animal proteins are “complete,” containing all the amino acids essential for survival. Humans need to get nine of these essential amino acids from their diet; dogs require ten: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine

Taurine is “conditionally” (sometimes) essential. Dogs make their own taurine from methionine and cysteine. But big dogs are less able to keep up with their own needs, and some individual dogs’ taurine production is impaired. All meat contains taurine, so dogs eating a diet that includes meat, poultry, fish or eggs are unlikely to become deficient. However, some meats contain less taurine. These include rabbit, kangaroo, and ruminant (beef, bison, lamb, venison) meats. By-products are considered low in taurine.

 Plants also contain protein, and many pet foods include plants that contribute protein as well as other nutrients to the formula.

Terms like meat, poultry, meals, and by-products have legal definitions that pet food manufacturers follow. Where relevant, we’ll take a special look at those terms.

Animal Sources Of Protein In Dog Food

Livestock, poultry, and seafood are major sources of today’s pet food ingredients. But by the time they are incorporated into the product on the shelf, these elements bear little resemblance to a whole rabbit, grouse, moose, or salmon. 

After a cow or pig or chicken is slaughtered, the carcass is hung head down and drained of blood. That blood is sold for a variety of purposes, including livestock feed and fertilizer. Next, the skin is stripped off (or in the case of poultry, de-feathered), and the carcass is divided into components. Parts that can be routed into the human food chain are separated. Around 45% of every slaughtered animal is not suitable for human consumption. Instead, it is used as animal food, including pet food. Other uses include fertilizer, pharmaceuticals, soaps, cosmetics, and lubricants.  


Meat is the most profitable portion of a slaughtered animal. Every effort is made to collect as much of it as possible. Human edible meat is turned into steaks, roasts, and other familiar cuts, as well as scraps that can be used in soups and stews. Mechanically separated non-beef meat, sometimes known as “pink slime,” involves bone-in meat run through a grinder and separator to remove bones. It’s found in products like lunch meat, sausage, hot dogs, baby food, and Spam.

Why not beef? It was outlawed for human consumption in 2004 in response to Mad Cow Disease, or Bovine Spongiform Encephalopathy (BCE). The bones, and what little meat is left clinging to them, may go to pet food and other uses.

“Meat” is a fresh (or frozen) product consisting of striated muscle (from skeletal muscle, tongue, diaphragm and esophagus) with or without attached skin, fat, and “sinew” (connective tissue). It cannot include bone. The term “meat” applies only to mammals, and is restricted to cows, sheep, goats, and swine. It is not processed (other than freezing) before its arrival at a pet food maker’s facility.

“Poultry” is the equivalent term applied to any kind of fowl raised for consumption. It’s restricted to meat, skin, fat, and – unlike mammals – bones. It excludes heads, feet, guts, and feathers.

“Fish” may include only a named species (such as salmon from a fish farm in the Puget Sound) or a mixture of species, such as “white fish,” where there may be a predominant species (typically tilefish), but other species aren’t excluded. Mars and Nestlé Purina have both been busted (twice now) for shark DNA in their canned cat foods. Shark meat is white, but it’s certainly not okay to kill endangered species for cat food. Fish are generally ground whole. However, commercial Pacific salmon (both farmed and wild-caught) are shipped to China for processing and could potentially end up in a batch of “fish” destined for dog food. 


Byproducts can be thought of as “parts that aren’t meat.” More specifically, “A by-product is defined as a secondary product obtained during the manufacture of a principal commodity… Approximately 49 percent of the live weight of cattle, 44 percent of the live weight of pigs, 37 percent of the live weight of broilers, and 57 percent of the live weight of most fish species are materials not consumed by humans.”

Byproducts have gotten a very bad reputation over the years. However, they’re not necessarily bad. Liver, heart, spleen, and other organs are by-products. Liver in particular is a great source of nutrients, including trace minerals and vitamins. 

Meat and poultry byproducts are “fresh,” meaning they go from the slaughterhouse to the pet food plant … although they may be frozen for long-distance transport. 

Meat byproducts are primarily the innards (lungs, spleen, liver, kidneys, lungs, brains), blood, bone, guts (without the poop), but excluding hair, horns, teeth and hooves.

Poultry byproducts may include (or consist solely of) heads, feet, and viscera (guts) “free from fecal contamination.” As if there is a guy whose job it is to squeeze all the poop from chickens’ guts before they’re shipped off. I do not want that job and neither do you – 8 billion chickens are eaten every year in the US. 

Rendered Meals

If an animal-source ingredient includes “meal” in the name, it’s a rendered product. The rendering process is simple: grind up the incoming materials, boil them for a while, skim off the fat, and dry the rest. The end result is a slightly greasy, brown, high protein powder. At that point, the inputs are indistinguishable. 

Meat meal (including beef meal, lamb meal, etc) is a rendered product. It is far less restrictive than “meat” and is defined as “mammal tissues.” It cannot contain added blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents … but there’s no requirement to remove those things before rendering. It may include bones, but there is an upper limit to the calcium content. 

Poultry meal (chicken, turkey, and other fowl raised for food) is rendered. It includes skin and muscle, with or without bone, excluding feathers, heads, feet, and viscera. Better foods will name the species, with a description like chicken meal or turkey meal

Poultry byproduct meal may include skin, muscle and bone, but also heads, necks, feet, and innards. Feathers are not allowed. 

Meat byproduct meal might as well contain ground unicorns, since it does not have a specific definition.

The mammalian equivalent of poultry by-product meal is meat and bone meal, so …

Is Meat And Bone Meal Good For Dogs?

No, it’s not. Meat and bone meal is a single ingredient, often abbreviated as MBM. It is not meat meal plus bone meal. It comes from mammals (any mammals), and things like horns, hides, and manure can’t be added, but that’s about the only limitation. MBM, and its generic rendered partner, animal fat, are the ingredients most likely to contain pentobarbital (euthanasia solution) and other drugs and contaminants. It is truly the bottom of the barrel. If you see it on a label (even as an “upscale” form like beef and bone meal or pork and bone meal), just step away. Avoid any foods with this ingredient. 

Where Are Rendered Products Used?

Rendered products are used primarily in dry kibble and extruded soft-moist foods. It is unusual for them to be found in other food forms, although they are used in a few canned foods. By avoiding dry food, you can avoid the worst ingredients in the pet food industry.

There are two types of renderers: captive (packer), and independent. 

  • Captive renderers are associated with a slaughterhouse and accept only materials from that source. 
  • Independent renderers can accept anything, including deadstock (animals that died on the farm or prior to slaughter), slaughterhouse waste, used fryer grease from restaurants, and dead animals from shelters. 

Now, just because an independent renderer processes the more unsavory bits doesn’t mean those bits end up in dog food. There are many other outlets for rendered materials. But it also doesn’t mean those bits aren’t in dog food. There is a 2022 lawsuit against a brand whose food was analyzed for DNA and was positive for dog. 

Rendered products obviously vary greatly in content and quality. Chicken meal from a rendering plant attached to a Tyson’s factory in Arkansas will contain only chickens and be (relatively) decent quality. 

However, a great deal of the meat, poultry, and fish used in pet food comes from Asia, notably China and Thailand (also a major source of fish products). Even chicken grown in the US is likely to have been shipped to China for processing. It is impossible to tell the true country of origin from the label. 

A great deal depends on manufacturers’ reputations. They, in turn, rely on the honesty of their suppliers. Unfortunately, neither group has proven itself entirely trustworthy over time.

RELATED: Meat in pet food: Is it really meat?

Plant Sources Of Protein In Dog Food

All plants contain protein in the form of enzymes, structural compounds, and functional components. But, while plants like soy, hemp, and quinoa are complete proteins for humans, they aren’t for dogs. Dogs need arginine, and many dogs need taurine.

Plants do not contain any taurine. A few species of algae have a little. Arginine is also relatively scant in plants, except for legumes, seeds and nuts. But meat, poultry, eggs, and fish are replete with arginine and taurine, reflecting the dog’s natural carnivore nature. 

Vegetables vary widely in their protein content, from 36% in soybeans and 5% in peas, to 2% in potatoes and 3% in corn. Legumes tend to be vegetables highest in protein. 

Despite the low protein contact of most veggies, pet food suppliers have ingeniously created high protein extracts of many vegetables, such as pea protein, potato protein, rice protein concentrate, and corn gluten meal. Since animal protein is the costliest ingredient, many manufacturers boost the protein content by using one or more plant protein extracts. 

Legumes (peas and beans) are popular ingredients in “grain-free” dog foods. (Peanuts and alfalfa are also legumes, but they’re rarely used in pet food.) They contain a fair amount of protein, a lot of gut-nourishing fiber, and very little fat. But for all plant products except soybeans, their main constituent is carbohydrate. Lentils, for instance, contain about 63% carbs and 25% protein.

Corn gluten meal, a popular ingredient in lower-end kibble, can contain up to 80% protein. Strangely, none of it is actually gluten. (AAFCO is considering changing the name to a more honest description.) 

While using plant proteins to offset the high environmental cost of meat sounds good on the surface, they are not without problems. Most importantly, they are not a complete source of protein for your dog … and they are high in carbohydrates, a nutrient your dog doesn’t need. Look for dog foods with more animal proteins and fewer plant proteins near the top of the ingredient list, to give your dog more of the foods he needs to be truly healthy


Donadelli RA, Aldrich CG, Jones CK, Beyer RS. The amino acid composition and protein quality of various egg, poultry meal by-products, and vegetable proteins used in the production of dog and cat diets. Poult Sci. 2019 Mar 1;98(3):1371-1378.

Jayathilakan K, Sultana K, Radhakrishna K, et al. Utilization of byproducts and waste materials from meat, poultry and fish processing industries: a review. J Food Sci Technol. 2012;49(3):278-293.

McWilliams J, The deadstock dilemma: Our toxic meat waste. The Atlantic. 2010 Aug 11. 

Meeker DL. Essential rendering. 2006: National Renderers Association

Spitze A. R., Wong D. L., Rogers Q. R., Fascetti A. J.. 2003. Taurine concentrations in animal feed ingredients; cooking influences taurine content. J. Anim. Physiol. Anim. Nutr. 87:251–262

USDA. What is Mechanically Separated Meat? https://ask.usda.gov/s/article/What-is-Mechanically-Separated-Meat-MSM


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