Human-Grade Dog Foods: Some Science

In the world of commercial dog foods, the term “human-grade” is an odd duck.

VERY ODD

The oddness occurs because the term “human-grade,” while in use on labels and in marketing materials, actually has no legal definition. Rather, the regulated terms that are used to delineate between foods that are processed, marketed and sold for human consumption and those that are intended for consumption by pets and other non-human animals are “edible” (humans can eat) and “inedible” (animals can eat). Still, when you see the words “human-grade” on a dog food package, these words do have important meaning and should be given careful consideration.

Why care? The distinction is an important one. Foods in the first category (“edible“) are handled, processed, transported and stored under a set of regulations that are specifically designed to keep products both nutritious and safe. Conversely, foods in the second category (the “inedibles”) enter a separate supply stream that is demonstrably more relaxed in its requirements for preserving nutrient value and preventing microbial contamination during handling and transport.

In a nutshell:

Edible = Highly regulated; safe to consume as food; ends up in your supermarket.
Inedible = Less intensely regulated; not considered safe for humans to consume as food; ends up in pet foods.

For obvious reasons, the terms edible and inedible, while technically correct, do not sit well with most pet owners. Enter the term “human-grade.” Although the Association of American Feed Control Officials (AAFCO) does not have a formal definition for this phrase, they have accepted its use in the pet food industry and allow it to be included on pet food labels provided the following standards are met:

“…..the term “human grade” represents the product to be human edible. For a product to be human edible, all ingredients in the product must be human edible and the product must be manufactured, packed and held in accordance with federal regulations in 21 CFR 110, Current Good Manufacturing Practice in Manufacturing, Packing, or Holding Human Food.”

The Human-Grade Label: The AAFCO requirements set the bar very high for including this claim on a pet food label. Still, a number of companies are meeting these standards and are producing human-grade dog foods of a variety of types, including dehydrated, freeze-dried, and fresh cooked/frozen. The underlying assumption with all foods that carry a “human-grade” claim is that because of the types of ingredients, regulatory oversight, sanitation methods, and processing that are used, the end product will be safer and of greater nutritional quality than other foods that do not carry a human-grade claim.

What do we know? However, do we know this to be true? Well, there are some published data showing that human-grade chicken ingredients are of higher quality compared with the rendered chicken meals that are typically used in extruded dog foods. I wrote about this research in an earlier Science Dog essay, “Tastes Like Chicken“. However, until recently, there have been no published studies of the nutritional value of commercial, human-grade, dog foods. A study of this type has just been published by the team of nutritionists at the University of Illinois Animal Sciences Department. Here is what they did:

The Study: The nutrient digestibility and energy content of a set of six commercially produced, human-grade, fresh-cooked dog foods, all produced by the company “Just Food for Dogs LLC“, were tested using a validated feeding assay. Each food included a different primary protein source (beef, chicken, fish, lamb, turkey or venison) plus a digestible starch source (potato, rice, squash or macaroni).

Results: Although the foods were all produced by the same company, there were several significant differences among the six products:

Total (dry matter) digestibility: The overall digestibility was high for three of the six foods – those containing chicken, turkey or lamb – with values betwen 78 and 82 percent. However, the digestibility values for the fish and venison diets were quite low – around 67 percent. In the dog food world, digestibility values less than 70 percent are considered to be quite low (and not a good thing). For example, dry matter digestibility values that have been reported for extruded dry foods (not made with human grade ingredients) typically range between 64 percent (low) to 85 percent of greater (high). Therefore, while the human-grade chicken, turkey and lamb foods in this study are considered to be moderately high in digestibility, the venison and fish foods had very low values – and certainly did not fare better than typical extruded foods. (This was a bit surprising).
Indispensable (essential) amino acid digestibility: Taken together, the digestibility values for all of the essential amino acids provides a direct measure of a foods protein quality. Interestingly, the amino acid digestibility values of these foods were all quite high, ranging between 79 and 93 percent. These values, on average, are higher than those typically reported for commercial dry dog foods (i.e. non-human-grade foods). What this means, practically speaking, is that while the foods were only moderately digestible overall, their protein sources and amino acid profiles reflect high quality protein sources and indispensable amino acid availability. So, what gives?
Dietary fiber: The explanation may have to do with the dietary fiber content. There were wide differences in total dietary fiber content among the six foods (between 4 and 14 percent Total Dietary Fiber). These differences were caused by the different carbohydrate sources used and may have accounted, at least in part, for the lower dry matter digestibilities (without a loss of protein digestibility) in the fish and venison foods. This effect was not considered to be detrimental by the researchers, since dietary fiber provides several gastrointestinal benefits to dogs.

Take Away for Dog Folks: The results of this study seem somewhat mixed. While the overall diet digestibilities of the six foods were not as high one would have expected, their amino acid profiles and availability data reflect high quality protein sources. When viewed collectively, the chicken-containing food tended to have the highest amino acid digestibility values while the food that contained lamb had the lowest. When compared with dry, extruded foods (that are not human-grade), the digestibility values for amino acids of these six, fresh-cooked, human-grade dog foods all tended to be higher, while dry matter digestibility (possibly due to the relatively high fiber contents of of the foods) were similar or lower.

Of course, there are reasons other than nutrient digestibility and protein quality that dog owners choose a dog food that is labeled “human-grade”. Some of these may be ingredient sourcing and handling, quality control, regulatory oversight, the use of Good Manufacturing Practices, and product safety – all of which can be important factors when selecting a dog food. For now, we have at least a bit of evidence suggesting that human grade, animal-source proteins do indeed provide high quality nutrition to our dogs.

Happy Feeding!

DINNER TIME AT THE CASES

Cited Study: Oba PM, Utterback PL, Parsons CM, Swanson KS: True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay. Journal of Animal Science 2020; 4:442-451.