Evaluating the “Meal” and Animal By-Products in Pet Food

Beyond marketing hype—what we know, and need to know, about protein ingredients in commercial dog foods. A deeper look at what’s in the type of food so many of us feed our dogs.

In May 2014, Nestlé-Purina, the largest producer of pet foods sold in the U.S., filed a lawsuit against Blue Buffalo dog food, a competitor. Among other things, the lawsuit alleged that Blue Buffalo’s marketing claims—that their foods contained no by-product meals—were false and disparaging to other companies’ products.

According to the report of a testing laboratory hired by Nestlé-Purina, at least a few varieties of Blue Buffalo dry extruded foods (kibble) did indeed contain poultry by-product meal, comprising as much as 25 percent of the meal in some of its products. As is the way of the modern pet food industry, within days, Blue Buffalo responded with a countersuit of its own, accusing Nestlé-Purina of defamation, unfair competition and false advertising.

Central to this public (dog) food fight was the belief, strongly promoted by Blue Buffalo, that chicken or poultry meals are superior to by-product meals in nutritional value, and that high-quality dog foods contain the former and reject the latter. (It is of interest to note that Nestlé-Purina sidestepped the nutrient quality issue in their lawsuit. Rather, they contended that Blue Buffalo had falsely promoted itself as being completely transparent to its customers.)

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Initially, Blue Buffalo responded to the allegations with denial. Both companies launched public-relations campaigns that included strongly worded letters to “pet parents” (i.e., consumers). However, in October, Blue Buffalo had to eat crow (meal?) when they announced that one of their suppliers, Texas-based Wilbur-Ellis, had mislabeled an ingredient, which resulted in the presence of poultry by-product meal in some of their foods.

In the words of Blue Buffalo’s founder, Bill Bishop: “So, while their customers were ordering and paying for 100 percent chicken meal, at times they were receiving shipments that contained poultry by-product meal. As a result, we have stopped doing business with this plant.”

What is the truth? Are by-product meals lower in quality when compared with meals? Should discerning dog owners avoid chicken or poultry by-product meal and choose only foods that contain chicken or poultry meal? And is this a reliable way to distinguish between high-quality dog foods and foods of lesser quality?

Perhaps the best place to start is with an understanding of what a “meal” is.

Meals, the Protein Ingredient

Every ingredient that goes into a dog food contains a unique set of essential nutrients that it contributes to the finished food. In commercially prepared dry (extruded) dog foods, various types of meals are used to provide protein. These meals can be classified in several ways.

First, a meal may be plant- or animal- based. Examples of commonly used plant-based protein meals are corn gluten meal, soybean meal and pea protein (or meal). In general, plant-based protein sources are an inexpensive source of protein and are found in foods marketed to pet owners interested in economy. The quality of these meals is moderate to low in terms of amino acid balance and digestibility, although several protein sources are used to ensure that all essential amino acid needs are met.

Animal-source protein meals, on the other hand, vary tremendously in both source—animal species—and in quality measures such as digestibility, amino acid content and amino acid availability. Examples of species-specific meals that are commonly used in pet foods are chicken, bison, beef, salmon, lamb, venison and turkey meals. These meals may also be classified more largely as poultry (contains varying amounts of chicken, turkey or duck), fish (contains multiple fish species), or meat (contains varying amounts of pork, beef or sheep).

Animal-source meals are commercially produced through rendering, a cooking process that converts slaughterhouse products that have been deemed unfit for human consumption into a form that is regulated as acceptable for use in pet foods. Generally, animal parts used for rendering are those not typically consumed in our Western diet: organ meats such as spleen, kidneys, liver; stomach and intestines; varying amounts of bone; and, in the case of poultry, necks, feet and heads.

In addition to slaughterhouse waste, “spent” layer hens from the egg industry and food animals found to be too diseased or injured to pass inspection for use as human foods may also end up at the rendering plant. Classified during the slaughter process as “inedible,” these parts are redirected into an alternate supply stream and are handled, transported and processed differently than those intended for human consumption.

During the rendering process, the combined components are ground, mixed and heated to a high temperature (220° to 270°F), which cooks the product, kills microbes and sterilizes the mixture. Sterilization is necessary because refrigeration is not required for the handling or transport of inedible foods.

The resulting slurry is then centrifuged at high speed to remove lipids (fat). The removed fat is further processed and eventually is sold separately as chicken, poultry or animal fat. The mixture that remains is dried and ground to a uniform particle size that ultimately has the appearance and texture of dry corn meal. Animal protein meals are very low in moisture and contain between 55 and 65 percent protein, making them a rich source of protein when included in a pet food.

From a commercial perspective, meals are well suited for use in dry foods because they can be stored and transported easily, and have the low moisture content necessary for extrusion processing. By comparison, high-moisture protein ingredients, such as “fresh” chicken (or other meat), contribute only small amounts of protein by weight to the end product because the water is cooked off during the extrusion process.

These ingredients may be listed first on a food’s ingredient list simply because they contain more than 60 percent water, and ingredients must be listed in predominance by weight at the time of processing. In reality, it is the dried meals, usually found within the first three to five ingredients on the list, that provide the bulk of dietary protein in dry dog foods.

Meals and By-Product Meals Defined

The term “by-product” is the designator receiving the most attention.

It is important to know that on pet food labels, this term is only applied to chicken and poultry meal. This distinction is largely bureaucratic; the Association of American Feed Control Officials (AAFCO) sets the definitions for ingredient terms, and they have not designated a by-product meal term for any other animal protein ingredient. The closest they’ve come is “meat” meals versus “meat and bone” meals; the latter contains bone, which can reduce its quality as a protein source.

So, what exactly is the difference between chicken (poultry) meal and chicken (poultry) by-product meal?

According to AAFCO, the term “meal” refers to the “dry, rendered product from a combination of clean flesh and skin with or without accompanying bone, derived from the parts of whole carcasses of [chicken/poultry], exclusive of feathers, heads, feet and entrails.” (AAFCO 2010)

Although this definition seems to suggest that meals are produced from the same parts of the chicken that make it to the supermarket for human consumption, this is not true. As mentioned previously, animal protein meals are produced from slaughterhouse waste and other food animals that are deemed “not for human consumption” (i.e., inedible).

In the case of chicken, this is the “chicken frame,” or what remains of a chicken’s body after the parts destined for human consumption have been removed. More than 70 percent of a broiler chicken ends up in the supermarket, leaving about 30 percent in the frame, which is made up of a bit of muscle meat plus a lot of connective tissue and bone. In fact, no meals are produced from edible (human-grade) meats because rendering plants are in the business of taking inedible animal parts and converting them into a form that can be fed to non-human animals.

Chicken (or poultry) by-product meal, on the other hand, is composed of the same chicken components that are included in meals, with the difference that by-product meals may also contain varying quantities of heads, feet and viscera (guts). Therefore, the difference between a chicken (or poultry) meal and its respective by-product meal is the inclusion of heads and necks, feet, and guts (viscera) in the latter and the exclusion of those body parts from the former.

On the face of it, this appears to be an obvious quality distinction. After all, any product that has heads, feet and guts in it not only sounds yucky, but certainly must also be of poor quality, right? Well … it depends.

Is One Better than the Other?

Given this definition, the general (and understandable) perception is that meals will be of higher quality than byproduct meals. This is clearly the conclusion that Blue Buffalo and other pet food companies that make “No By-Products!” claims on their labels are banking on.

However, consistent and substantial quality differences between the two ingredient types are not reported. The fact is that the inclusion of additional body parts (heads, feet and guts) in by-product meals can reduce, maintain or improve the quality of a meal. (Aldrich, Daristotle 1998)

These three additional parts, although certainly not very appetizing to most people, have varying nutritional value as food ingredients.

First, the protein quality of viscera (internal organs and intestinal contents) is similar to that of chicken flesh components included in very high-quality chicken meals (and to what humans consume in a chicken dinner). In other words, including organ meats and intestinal contents in a byproduct meal does not negatively affect the meal’s protein quality and may even improve it in a poor- or average-quality meal.

Second, the inclusion of chicken heads in the mix results in a slight reduction in nutritional quality. This is because chicken brains are highly digestible while chicken skulls, being bone, are less so. So it appears to be a zero-sum game when it comes to the added chicken heads.

Last, chicken feet. As a food ingredient, feet are simply bad and have measured quality values similar to feeding connective tissue or bone residue. (This doesn’t stop them from being thoroughly enjoyed in some cultures, however.)

So, collectively speaking, including additional body parts in a by-product meal may affect the resultant product’s protein quality either positively or negatively when compared with its corresponding meal. How, and how much, they affect it depend largely upon the actual proportion of the three different body parts that are included in the end product. If there are lots of guts, quality improves. Heads: could go either way. Feet: bad news. Specifics on the type and quantity of these additions is, by the way, information that a consumer is never privy to.

Why All the Hype?

Studies of the digestibility and protein quality of meals and by-product meals have found that as a group, meals are slightly more digestible and contain slightly more available essential amino acids than their associated by-product meals. (Locatelli, Howhler 2003; Cramer, et al. 2007)

However, there is also a lot of overlap between the two ingredient groups, meaning that a given meal may be better, equal to or even lower in quality than a given by-product meal. Overall, the differences that have been found are neither dramatic nor worthy of the hysteria that seems to accompany the word “by-product” among dog owners and some pet food companies.

Therefore, the marketing hyperbole and excessive “patting oneself on the back” by companies that include meals but not by-product meals should be viewed by all dog owners with a hefty dose of skepticism. True, there is some difference, but probably not enough of a quality difference to warrant the inflammatory language and excessive claims that are being made by companies jumping on the by-product-free bandwagon.

Ironically, consumers have no direct way to know if the meal used in the food they select is of low, moderate or high quality, let alone the extent of the difference between a given meal and a by-product meal. Moreover, there is no evidence showing one way or another if the measured and reported differences between chicken meals and chicken by-product meals have an effect upon dogs’ overall nutritional health.

I would suggest that this exaggeration of difference has occurred (and been actively promoted) because there are so few available ways for dog owners to accurately assess the quality of ingredients in commercial pet foods. As a result, this single AAFCO-defined difference (meals vs. by-product meals) has caught on like a house on fire, with marketing campaigns flinging additional gasoline to fuel the flames and causing this distinction-without-a-difference to garner more importance than it warrants.

What We Know—and Don’t Know

It is an unfortunate paradox that one of the most important nutrients for dogs (protein) is supplied by a type of ingredient (protein meals) that consumers have almost no way of evaluating. This is especially concerning given that animal-source meals can vary tremendously in the components that make them up and, ultimately, in their quality (i.e., in nutrient content and digestibility). What information is available for consumers, and what is hidden from us? Sadly, there is much more of the latter than the former.

Animal-source proteins are generally better balanced in terms of amino acid content when compared with plant-based proteins and should be the preferred sources of protein in a quality diet. When assessing animal-source protein meals, choosing a meal from a named species is somewhat helpful. When you see a named species—chicken, beef, salmon, duck or bison, for example—as the major protein meal ingredient, it generally indicates that the food is of higher quality (or at least a better-regulated product).

Ingredient supply companies are required to keep these ingredient streams separate and designated, which means that sources are not mixed and translates to a more uniform product and greater regulatory oversight.

Conversely, the generic term used to describe a group of food animals (poultry, meat or fish meal), means that the meal may contain a mixture of species with no guarantee of any particular animal species or proportions in a given meal. At the production level, this also means that several ingredient streams are combined, with varying sources of origin, regulatory oversight and quality attributes.

Additionally, the species source that is least expensive in the marketplace at a given point in time may increase in proportion in its respective meal. Because of these differences, generic (combined) meals are less expensive for pet food manufacturers than are species-specific meals.

The fact that these three designators—plant- vs. animal-source, species vs. generic and meal vs. by-product meal (for chicken/poultry)—are the only protein-ingredient quality designators available to consumers might not be an issue if they were in truth the most important quality differences among animal protein meals. However, they are not. Animal protein meals differ in ways that are invisible to consumers and can significantly influence the quality of the foods in which they are used.

Animal-source protein meals contain varying amounts of bone and connective tissues (this pertains to both meals and by-product meals), which affect the product’s protein quality and mineral balance. Bone matrix and connective tissues contain the protein collagen, which is poorly digested and utilized when included as a dietary protein source, and bone contributes excess amounts of calcium and several other minerals. Meals that are high in collagen and minerals from bone and connective tissues are of lower quality than those that contain a larger proportion of muscle meat.

Because inedible food products are not refrigerated or subject to the same handling regulations as foods destined for human consumption, both the handling and transportation of raw materials can affect the quality of the end product. If rendering is conducted at the slaughterhouse of origin, the meal is usually produced within a day or two following slaughter.

However, when raw materials are transported to a rendering plant in another location, time spent during transport under unrefrigerated conditions can lead to increased microbial contamination and oxidative damage.

Differences among rendering plants also exist and are important for the end product. High temperatures or excessively long cooking can damage a meal’s protein, making certain essential amino acids less digestible and available.

Finally, as seen with the Blue Buffalo case, pet-food companies are at least somewhat dependent upon the integrity and honesty of their ingredient suppliers. A division within the animal feed industry designates some meals as pet-food grade and others as feed grade, with the former containing a lower percentage of ash (minerals). (Dozier, et al. 2003)

In addition, some pet-food companies select only meals that meet a particular standard, while others impose additional refining methods on their protein meals to increase digestibility and improve protein quality.

Various analytical tests are used to measure a meal’s digestibility and amino acid availability, and many pet-food companies also routinely measure the digestibility of their foods using feeding trials. However, this information is not easily available to consumers, and pet-food companies are under no obligation to accept or reject meals of different quality levels or to share such information with consumers.

To date, there is no way for pet owners to differentiate between dry dog foods that use high-quality animal protein meals and those that use poor quality meals, other than the cost of the food and the three designators discussed previously. You can contact the company and specifically ask for information about the food’s protein digestibility and quality, of course.

However, you may be disappointed. While researching my book, Dog Food Logic (2014), I contacted the manufacturers of more than 30 different pet-food brands and requested protein and diet digestibility information for each of the products. I received no reply at all from the majority of companies and useful information for just two of the brands.

Are there other options? In today’s innovative market place, there are indeed a few. Two other animal-source protein ingredients (in addition to fresh meats prepared at home) are those that are either freeze-dried or dehydrated.

Freeze-dried ingredients are typically used in raw food diets, but can also be cooked prior to packaging. Dehydration usually uses heat treatment to kill microbial growth and so moderately cooks the meat. These sources are likely to be of higher quality and digestibility because they have not undergone the high heat processing that meals are subjected to.

If they are human-grade meats, all the better, as this means that the ingredients and the end-products were handled and produced using the same regulatory oversight as required with human foods. However, with a few exceptions, neither freeze-dried nor dehydrated meat sources are routinely used as the primary protein source in dry, extruded foods.

Nor have I found a source of dried protein meals produced using human grade (i.e., edible) meat sources and human food processing methods. To do so (and to promote them as such) would add a dimension of choice and distinction regarding the quality of dry dog food that does not exist today.

Dry extruded dog food continues to be the most popular type of dog food sold in the U.S., and I believe such products would be welcomed by owners willing to pay a bit more for a better-regulated and higher-quality food.

While rendered animal meals can be of high quality and can provide an excellent protein source in dry dog foods, if an animal-source meal has been poorly sourced, handled, processed or regulated, its protein can be damaged, making it a poor source of essential amino acids for dogs and reducing the digestibility and quality of the entire diet.

Unfortunately, there is no way for consumers to tell from a food’s label if the meal used is of high, moderate or low quality. Because meals make up the bulk of protein in dry dog foods, information about their quality, and by extension, how nourishing they are, is the most important consideration that we should be concerned with when we look at an ingredient list.

The problem is, despite what companies beating the “No By-Products” drum would like us to believe, we have no way of knowing which animal protein meals are better than others.