What I mean of course, is “What’s in your dog’s food?”
When asked this question, most owners read the list of ingredients found on their food’s label. By law, pet food ingredients must be reported in descending order of preponderance by weight at the time of processing. This means that ingredients that are found first in the list are present in greatest abundance in the food.
There are a number of limitations regarding the type of information that a pet food ingredient list provides to consumers; most of these are detailed in my book Dog Food Logic. However, until recently, it was generally presumed that misrepresenting food ingredients, for example listing an ingredient that is not actually present in the food or failing to identify others, was not one of those limitations. Unfortunately, such a presumption may be ill-founded.
Several research studies published in the scientific literature over the past four years have shown that at least some brands of commercial dog foods have ingredient lists that do not always conform to what is actually in the food.
Study 1: Four brands of dry dog food that are marketed as novel protein source diets containing venison were tested for the presence of other protein sources (1). Of the four products, two listed chicken and one listed rice protein in addition to venison on their label ingredient panel. Results: Of the four foods, three tested positive for the presence of soy protein and one tested positive for the presence of beef protein. In all of these cases, neither beef nor soy products were reported in the product’s ingredient list. (It is interesting and somewhat ironic to note that one of the foods that tested positive for soy protein carried a front label claim stating “No Soy!”).
Study 2: The same team of researchers tested four retail dry dog foods that carried a “No Soy” label claim and seven therapeutic dry foods marketed to veterinarians for use in diagnosing soy allergies in dogs (2). Results: Soy protein was detected in three of the four retail brands. Of the seven veterinary-prescribed foods, four were found to contain low levels of soy protein.
Study 3: Eleven limited ingredient diets (LIDs) and one veterinary-prescribed hydrolyzed protein food were tested for the presence of animal origin ingredients not reported on their ingredient label (3). This study used DNA analysis and microscopic analysis of food particles that allowed the distinction between mammal, fish, and bird tissues. Results: Of the 12 products, the species of animal identified by microscopic and DNA analysis matched the food label’s ingredient list in only two. In the remaining 10 products, bone tissue fragments from one or more unreported animal source proteins were present.
Study 4: Most recently, a comprehensive study published in the journal Food Control examined the content of 52 brands of commercial dog and cat food using DNA analysis. Results: Of the 52 products, 31 (60 %) had no labeling violations, meaning that the protein ingredients that were reported in the ingredient list completely matched the sources that were identified via DNA analysis. However, 21 brands (40 %) contained protein sources that were not listed on the ingredient list or in one case, a protein source that could not be identified. In three of these products, the protein source listed on the ingredient panel was entirely absent from the food. Chicken was the most commonly undeclared protein source in the mislabeled foods. This is not surprising because chicken is generally the least expensive source of animal protein in pet foods. Mislabeling was also more frequently observed in canned (wet) pet foods than in dry pet foods. The presence of goat meat (yes, you read that correctly) was found in 9 products. Seven of these identified another animal species source such as chicken or beef on their label and did not include the more generic “meat” term nor (obviously) “goat meat” as an ingredient.
Take Away for Dog Folks: The authors of the first three papers wrote that their objectives were to examine LIDs for the presence of undeclared protein ingredients. Their concern was the increased use of these foods by owners and some veterinarians to diagnose food-related allergies in dogs. If you are not familiar with it, the standard diagnostic approach when food allergy is suspected is to feed a food that contains a single and novel (or hydrolyzed) protein source to the dog for 8 to 10 weeks. This is called an elimination diet and its purpose is to prevent exposure to all potential food allergens. If a dog’s signs diminish, the elimination diet trial is considered positive for adverse food reaction (food allergy) and an attempt is made to identify protein sources that the dog can tolerate. The scientists’ concern was that owners were unwittingly using the LIDs as an alternative to the more expensive and supposedly better controlled veterinary-prescribed foods. The expectation was that the therapeutic foods would contain only what their labels claimed, while the retail LIDs would be contaminated with other ingredients. What they found however, was that both retail foods and veterinary-prescribed foods have the potential to be mislabeled. (Oops).
Regardless of results not always showing what one expects, there are several important issues that these studies expose:
- Intentional or accidental? The analytical tests used in these studies are able to detect very small quantities of undeclared protein sources. Therefore, a positive result does not necessarily mean that the source was contributing a large proportion of the food’s protein. It only means that an undeclared protein source was present. This might occur accidentally as a result of ingredient cross-contamination during transportation, via airborne particle transfer in the manufacturing plant, or through the use of equipment that was not thoroughly cleaned between production runs. Regardless of intent, these causes are still problems and should be addressed in good manufacturing practice and quality control procedures. Alternatively, the identification of chicken as the most frequently undeclared animal protein source certainly suggests the potential for intentional substitution and mislabeling, seeing that chicken is less expensive than the ingredients that it augmented or replaced. Because these studies did not investigate the quantities of undeclared ingredients or whether or not their presence was intentional, these are questions that still need to be answered.
- Diagnosing/managing allergic dogs: For those who live with dogs suspected of having a food allergy, these results are bad news regardless of knowing quantities or intent. Although the concentration of a food allergen that is needed to trigger an allergic response in dogs is not known, it is expected to be similar to that in people – very low. These studies suggest that feeding a veterinary-prescribed elimination diet may not be a guarantee that the dog is not exposed to a suspected allergen such as soy. In addition, feeding a dog a retail brand LID may not be an effective approach even when food allergens have been identified. For these reasons, some veterinarians and nutritionists recommend feeding a homemade elimination diet for the diagnosis of food allergies in dogs. Once the allergenic protein is identified, extreme care will be needed during food selection.
- Trust: Last, but certainly not least, are the issues of food mislabeling, manufacturing integrity and consumer trust. The cases reported in the most recent study, in which listed ingredients were completely absent from some foods and were substituted with other protein ingredients, are in clear violation of AAFCO labeling regulations. The researchers of that study had purchased the sample foods from retail vendors, which indicates that these violations are occurring without detection. What is not known is whether ingredient substitutions, additions, and mislabeling are intentional or accidental or where within the production chain these adulterations are taking place. What does seem clear however, is that consumers cannot always trust the ingredient list to represent only and all ingredients that are present in the food.
What is a dog person to do?? Remember that a substantial proportion of products that were tested in these studies contained all and only those protein ingredients that their labels reported. They were not mislabeled. If you feed commercial dog food, seek out reputable manufacturers. These are the producers who provide ingredient source information, manufacturing details, safety records, and detailed product information to their consumers. Moreover, ask questions, request information, demand transparency and be a critical thinker (and consumer) for your dog so that you have a better chance of knowing what is in YOUR (dog’s) food.
- Raditic DM, Remillard RL, Tater KC. ELISA testing for common food antigens in four dry dog foods used in dietary elimination trials. Journal of Animal Physiology and Animal Nutrition 2010; 95:90-97.
- Willis-Mahn C, Remillard R, Tater K. ELISA testing for soy antigens in dry dog foods used in dietary elimination trials. Journal of the American Animal Hospital Association 2014; 50:383-389.
- Ricci R, Granato A, Vascellari M, Boscarato M, Palagiano C, Andrighetto I, Diez M, Mutinelli F. Identificatin of undeclared sources of animal origin in canine dry foods used in dietary elimination trials. Journal of Animal Physiology and Animal Nutrition 2013; 97:32-38.
- Okuma TA, Hellberg RS. Identification of meat species in pet foods using a real-time polymerase chain reaction (PCR) assay. Food Control2015; 50:9-17.