Dog and Cat Foods

On the label, the guaranteed analysis lists the minimal percentages of crude protein and crude fat and the maximal percentages of water and crude fiber on an as-fed (not dry-matter) basis. This analysis does not specify the actual amount of protein, fat, water, and fiber in the product. Instead, it indicates the legal minimums of protein and fat and the legal maximums of water and crude fiber content contained in the product. The percentage of crude fiber only is an estimate of insoluble fiber and does not include soluble fiber contents.

A laboratory proximate analysis lists the actual nutrient concentrations in the food, and two foods that have identical guaranteed analyses may have very different proximate analyses. A guaranteed analysis for protein may list a minimal level of 25%, while the product may (and usually does) contain > 25%. A certain variance above or below a minimum or maximum should be expected. Consequently, whenever possible, the manufacturer’s average nutrient profile should be used to evaluate a food.

Direct product comparisons made between like (similar water content) products (ie, dry versus dry, or canned versus canned) are generally valid. However, comparisons across different food types should be made on a dry-matter or caloric basis.

A way to compare two diets from the information contained in the guaranteed analysis is to calculate the approximate percentage of dry matter of a nutrient in a product. This entails first calculating the dry matter in the diet by subtracting the moisture percentage listed in the guaranteed analysis from 100%. Next, calculate the percentage of the nutrient of interest on a dry-matter basis using the following equation: (% nutrient [as fed]/% dry matter in diet) × 100 = ~% of nutrient (dry matter). The following is an example comparing the percentage of protein in a diet on a dry-matter basis from a dry product and a canned product:

1. Calculate percent dry matter in diet: Diet A: 100% −12% = 88%; Diet B: 100% − 82% = 18%

2. Calculate percent protein dry matter:

Diet A:    Protein (as fed)  =  24% / 88% × 100 = 27.3% protein on a dry-matter basis

Diet B:    Protein (as fed)  =    8% / 18% × 100 = 44.4% protein on a dry-matter basis  

In the US, all pet foods sold must be registered with state feed control officials and must contain approved ingredients generally regarded as safe, unless they are for specialized purposes, such as the amelioration or prevention of disease. Such foods are considered to be drugs and must be approved by the FDA.

Ingredients are listed in descending order of weight, on an as-fed basis, in the food. Although a food ingredient (eg, chicken) may be listed first, if that ingredient is 75% moisture, it will contribute a much smaller percentage of total nutrients to the food dry matter than the same ingredient added in a dry form (eg, chicken meal).

In addition, an ingredient such as wheat may be listed by individual type, eg, round wheat and wheat flour. In this case, the total amount of wheat in the diet may be a large portion of the total food dry matter; however, when presented as individual types based on fineness of grind, each type of wheat appears lower on the ingredient list. This is referred to as ingredient splitting.

No reference to quality or grade of an ingredient is allowed to be listed; therefore, it is difficult to evaluate a product solely on the basis of the ingredient list. The value of comparing ingredient lists is limited; instead, the focus should be on analyzing nutrient contents of the diets because animals require nutrients and not ingredients.

The ingredient list may be useful when evaluating patients experiencing an adverse reaction to a food, possibly due to an allergy or intolerance to one or more ingredient sources such as beef, wheat, etc. However, if the diet is an over-the-counter product and produced in a plant where other ingredients are used, often these diets can contain trace amounts of other ingredients that are not listed on the label. For example, trace amounts of other ingredients could be in the machinery used to process foods or airborne in the plant. For example, there are warnings on foods intended for humans that state things such as "this product was also produced in a plant that used peanuts, eggs, etc."

As a result, choosing a diet to rule out an allergy to a certain ingredient may be best done using a therapeutic diet, where the pet food company has taken extra precautions to ensure that there is no cross contamination with ingredients not listed on the label, or a complete and balanced homemade diet formulated by a boarded veterinary nutritionist.

Dog and cat food labels must include a statement of nutritional adequacy or purpose of the product except when a product is clearly identified as a snack, treat, or supplement. This statement indicates if the food is not meant for longterm feeding, or alternatively if it provides all the nutrients required for a dog or cat, and also what life stage it is intended for. The Association of American Feed Control Officials (AAFCO) recognizes four categories: growth, maintenance, gestation/lactation, and all life stages. The term “all life stages”on a label indicates that the product has been either formulated or tested for gestation/lactation, growth, and adult maintenance.

If the label contains a statement with the words “complete and balanced," "100% nutritious," "perfect," or "scientific," this indicates that the product contains all nutrients presently known to be required by a specific species and life stage and that the nutrients it contains are properly balanced to the energy density of the diet. There are cautions “against the use of some of these requirements (levels) without demonstration of nutrient availability” because some of the requirements are based on studies in which the nutrients were supplied as purified ingredients and, therefore, are not representative of ingredients used in commercial pet foods or there is potential for nutrient interactions within a diet that impact availability. Laboratory analysis does not address the issue of bioavailability of nutrients.

There are four possible AAFCO nutritional adequacy statements, and one of them must appear on all pet food labels. If the diet states that it is complete and balanced, then it must contain verbatim one of the first three statements substantiating how it was determined that the product was complete and balanced:

1. "(Name of product) is formulated to meet the nutritional levels established by the AAFCO Dog (or Cat) Food Nutrient Profiles for (_____)." The blank is to be completed by using the stage or stages of the pet's life, such as gestation/lactation, growth, maintenance, or the words "all life stages"). For a dog food that states it is intended for "growth" or "all life stages," then one of the following phrases must also be added verbatim to the end of the claim:

   • "including growth of large-size dogs (70 lb [32 kg]. or more as an adult)" if the product has been formulated to meet the levels of nutrients specifically referenced in the Dog Food Nutrient Profiles as being applicable to large-size growing dogs, which currently only applies to calcium

   • "except for growth of large-size dogs (70 lb [32 kg] or more as an adult)" if the product has not been formulated to meet the levels of nutrients specifically referenced in the Dog Food Nutrient Profiles as being applicable to large-size growing dogs

2. "Animal feeding tests using AAFCO procedures substantiate that (Name of Product) provides complete and balanced nutrition for (_____)." The blank is to be completed by using the stage or stages of the pet's life, such as gestation/lactation, growth, maintenance, or the words "all life stages."

3. "(Name of Product) provides complete and balanced nutrition for (_____) and is comparable in nutritional adequacy to a product which has been substantiated using AAFCO feeding tests." The blank is to be completed by using the stage or stages of the pet's life, such as gestation/lactation, growth, maintenance, or the words "All Life Stages." This statement indicates that the product is a member of a product family which has already been nutritionally analyzed.

4. The statement "This product is intended for intermittent or supplemental feeding only" is required if a product does not meet the requirements for being a complete and balanced diet or any other special nutritional or dietary need and is suitable for only limited or intermittent or supplemental feeding.

Feeding guidelines must be expressed in common terms, such as “feed (weight/unit of product) per (body weight of dog or cat).” The frequency of feeding must also be specified. The guidelines are general recommendations at best, and body weight and body condition must be monitored to prevent over- or underfeeding.

The statement of calorie content must appear under the heading "Calorie Content" and be used in terms of metabolizable energy (ME) on an as-fed basis. It must be expressed both as "kilocalories per kilogram (kcal/kg) of the product," not kg of the animal, and as "kilocalories per familiar household measure (eg, cans or cups) or unit of product (eg, treats or pieces)."

If a product includes the terms "light," "lite," or "low calorie," or words of similar designation, then it must meet specific criteria pertaining to kcal ME/kg of diet, depending on the moisture content of the diet. If a product uses the terms "less" or "reduced calories" or words of similar designation, it must include on the label the name of the product of comparison and the percentage of calorie reduction. The calorie content of the diet must also be stated as listed above.

Dry food is the most popular category of pet food in the US and some other countries. Dry foods generally contain ~90% dry matter and 10% water. Approximately 95% of dry dog and cat foods are made using extrusion, ie, they are made by combining and cooking ingredients (grains, meat and meat by-products, fats, minerals, and vitamins), then forcing the mixture through a die, where a knife slices the mixture to determine the shape and size of the kibble.

During cooking and extrusion, temperatures used by manufacturers may vary between ~80ºC and 200ºC (~176ºF–392°F). A minimum cooking temperature of 130ºC (266ºF) is required to kill both microbes and bacterial spores in food. Cooking temperatures used in producing pet food are consistent with temperatures used in cooking foods intended for humans.

Advantages of dry food include lower cost than canned or semimoist food and the ability to store unused portions at room temperature. Certain specially formulated dry foods may also provide beneficial massage of the teeth and gums to help decrease periodontal disease.

Canned dog and cat foods contain 68%–78% water and 22%–32% dry matter. Many of the same ingredients are used in canned and dry foods, though not always in the same form. Given their high moisture content, canned foods typically contain higher amounts of fresh or frozen meat, poultry, or fish products, and animal by-products.

Many canned pet foods contain textured proteins derived from grains, such as wheat or soy. These materials function as meat analogues, having a physical structure similar to that of meat and high nutritional quality. The use of meat in combination with some of the textured proteins not only controls costs but can improve the overall nutritional profile of the final product.

Canned pet food processing begins with blending meat or meat analogues and fat ingredients with water and dry ingredients, such as vitamins and minerals, for proper nutrient content. The mixture is blended and sometimes ground to produce a fine slurry, depending on product profile. After cans are filled, they are sealed and retorted (a heat and pressure-cooking process that also sterilizes the contents), assuring destruction of foodborne pathogens. Advantages of canned food include a long shelf life in a durable container and high palatability. However, canned food is more expensive than dry food.

Semimoist dog and cat foods contain 25%–40% water and 60%–75% dry matter. They do not require refrigeration and are preserved using humectants—substances that bind water so that it is unavailable for bacteria and mold growth and assure shelf life. These formulations include simple sugars (usually sucrose), sorbitol, and salts. Many semimoist foods are acidified using phosphoric, malic, or hydrochloric acid to further inhibit spoilage.

Advantages of semimoist foods include convenience, high energy digestibility, and palatability. However, semimoist food is more expensive than dry food.

Dogs and cats can be successfully maintained on properly formulated home-cooked diets. Advantages of home-cooked diets include the use of ingredients chosen by the owner. Disadvantages include preparation time, variable quality control and diet consistency, higher cost, and the difficulty in formulating and preparing a nutritionally complete and balanced diet.

It is most difficult to formulate a nutritionally complete and balanced diet with sufficient nutrient density in a small volume of food that is palatable for cats. Many home-cooked diets result in foods that are high in protein and caloric density. If owners choose to feed a home-cooked diet, they should use a recipe formulated by a boarded veterinary nutritionist (versus a recipe found on the internet or in a book). It is also important to realize that no home-cooked diets have undergone the testing and research used to formulate some complete and balanced commercial pet foods.

Raw meat–based diets (RMBDs) have received a lot of attention in recent years. Proponents of raw diets often cite that raw meat–based diets are the evolutionary diet of dogs and cats and that domestic dogs and cats have never evolved into being able to digest and absorb commercial pet foods. Advocates also claim benefits ranging from improved longevity to superior oral health, general health, and even disease resolution.

The lack of high-quality research on these diets makes it difficult for veterinarians to make informed recommendations to pet owners regarding this feeding practice. However, a number of organizations have developed statements discouraging the feeding of raw or undercooked animal-source protein to dogs and cats, including the following:

• the American Animal Hospital Association (AAHA)

• the National Association of State Public Health Veterinarians (NASPHC)

• the American Association of Feline Practitioners (AAFP)

• the American Veterinary Medical Association (AVMA)

• the CDC

• the FDA Center for Veterinary Medicine (FDA CVM)

• the Canadian Veterinary Medical Association (CVMA)

There are two main types of RMBDs: home-prepared and commercial. In addition, a variety of raw dried or freeze-dried pet treats fall under this category. Home-prepared diets include a variety of feeding regimens, including BARF (bone and raw food or biologically appropriate raw food), the Ultimate diet, and the Volhard diet. Commercial raw meat–based diets most commonly are fresh, frozen, pasteurized, or freeze-dried. Some of these commercial diets are formulated to meet AAFCO nutrient profiles, but many are not.

One of the biggest areas of controversy surrounding these types of diets is the safety of these diets to not only the pets consuming them but to the pet owners and others who are exposed to the animals consuming them. Nutrient imbalances, dental injury, gastrointestinal obstruction or perforation, and exposure to pathogens are all risks associated with RMBDs.

Even if a pet owner takes precautions while handling and preparing these diets, the Salmonella contamination rates for beef and pork intended for human consumption are estimated to range from 3.5%–4%. Animals fed uncooked diets may become clinically ill as a result or may shed these pathogens in their feces, thereby exposing humans in the home environment(1, 2). Raw meat may contain other potential zoonotic pathogens, including the pathogenic strain of E coli O157:H7, protozoa, and nematodes.

Some commercial RMBDs are frozen or freeze-dried; however, neither freezing nor freeze-drying destroys all the potential pathogens and spores in these products. Some commercial raw meat–based diet manufacturers now use high-pressure pasteurization in an attempt to decrease the risk of pathogens. Although this process can decrease the numbers of many pathogens, it usually does not completely eliminate them, and bacteria and viruses vary in their susceptibility to this process.

It is illegal in the US to sell any commercial pet food that is contaminated with Salmonella, and numerous commercial raw diets and pig ears have been recalled by the FDA since 2017 due to potential contamination with Salmonella as well as Listeria. While commercial pet foods have also been recalled during that time for various reasons, the number of raw diets recalled relative to their market share has been much higher than for cooked commercial diets.

Veterinarians must also consider the potential legal implications of recommending raw meat–based diets. While zoonotic risks can be associated with feeding both commercial and home-prepared diets, if a pet owner, for example, develops a Salmonella infection from feeding a contaminated commercial diet, the pet food manufacturer is generally at risk of legal action. However, veterinarians who recommend home-prepared raw meat–based diets are potentially liable if an owner becomes sick from preparing these diets or as a result of pets shedding pathogens in their feces.

1. van Bree FPJ, Bokken GCAM, Mineur R, Franssen F, Opsteegh M, van der Giessen JWB, Lipman LJA, Overgaauw PAM. Zoonotic bacteria and parasites found in raw meat-based diets for cats and dogs. Vet Rec. 2018 Jan 13;182(2):50. doi: 10.1136/vr.104535. PMID: 29326391.

2. Ahmed F, Cappai MG, Morrone S, Cavallo L, Berlinguer F, Dessì G, Tamponi C, Scala A, Varcasia A. Raw meat based diet (RMBD) for household pets as potential door opener to parasitic load of domestic and urban environment. Revival of understated zoonotic hazards? A review. One Health. 2021 Sep 16;13:100327. doi: 10.1016/j.onehlt.2021.100327. PMID: 34584928; PMCID: PMC8455362.