Today, we take another look at a growing category of commercial dog foods – those carrying a human-grade label claim. Remember that the inclusion of this claim on a dog food label requires that the entire food not only contain human-grade (i.e. edible) ingredients, but also that it has been produced under the same regulations that oversee the production and transport of human foods.

Although this is a high bar to clear, a small number of pet food companies are producing these foods, in a variety of forms.

Are There Quality Differences?

This is the big question, of course. Although only a few studies have been conducted, there is evidence that both processing and ingredient source are important criteria to consider when comparing a human-grade dog food to other foods.

One study showed that amino acid availability (a measure of protein quality) in raw or moderately-processed chicken was significantly greater than the amino acid availability of rendered chicken meal, the processed form of chicken included in most extruded foods. The difference was so great that the rendered meal was estimated to be deficient in one or more essential amino acids if fed to dogs (see “Tastes Like Chicken“).

Last year, another study compared a set of six human-grade foods, all produced by the same company (Just Food for Dogs). The researchers reported amino acid availability values that were similar to the chicken ingredients study, signalling that the foods included high quality protein sources. However, while this study provided valuable information, it was not a feeding study with dogs. Rather, it used an accepted (and validated) rooster assay that is correlated with dog data. In addition, the study did not directly compare the human-grade products with commercial foods made with pet-grade ingredients.

New Study

Lucky for us, the same group of researchers recently conducted a study that fed the foods to actual dogs and also compared the human-grade foods to other (pet-grade) products. Here is what they did:

Study Format: The researchers compared two human-grade dog foods (Beef/Potato and Chicken/Rice; Just Food For Dogs) with a pet-grade extruded food (Blue Buffalo Life Protection Formula Chicken and Brown Rice Recipe) and a pet-grade fresh-cooked food (Freshpet Roasted Meals Tender Chicken Recipe). Using a study design called a replicated 4 x 4 latin square, 12 dogs were fed the diets for 28-day periods, on a rotated basis. Measurements included fecal characteristics, nutrient digestibilities, gut microbiota/metabolites, and standard blood serum health measurements.

Results: Several significant findings were found when the four foods were compared:

• Consumption: The dogs readily consumed all four products and remained healthy throughout the study period. However, dogs needed to eat significantly more food (dry matter basis) when fed the extruded food compared with when they were being fed the other three foods.
• Digestibility Differences: The digestibility values (dry matter, organic matter, fat) of the two human-grade foods were significantly greater than the digestibility values of both pet-grade products. Digestibility of the fresh cooked pet-grade food was higher than that of the extruded pet-grade food.
• The Scoop on Poop: All four of the products resulted in optimal stool quality scores. However, feeding the human-grade products resulted in much lower total fecal output compared with feeding the extruded or fresh-cooked foods.
• Gut Microbiota: A number of qualitative and quantitative differences in fecal microbiota values were found when dogs were fed the human–grade foods. The researchers attributed these differences to nutrient content, ingredient source and processing differences among the foods. However, conclusions regarding what, if any, health implications these differences may have are not yet possible. Dogs, like other species, demonstrate wide ranges in healthy gut microbiome populations that are highly influenced by diet.

Take Away for Dog Folks

Digestibility Matters

Perhaps the most impressive numbers in this study are the digestibility values. The two human-grade foods were rock stars in terms of digestibility – 91 percent for both foods. This can be compared with the very respectable value reported for the fresh cooked food (87 %) and the moderate value reported for the extruded product (81.5 %). The high values in the two human-grade foods are most likely a result of ingredient quality (human-grade vs. pet-grade) and processing method (gentle cooking vs. extrusion).

Although these two factors (ingredient quality and processing method) were not separated out using a balanced treatment design in this study, these results provide some insight regarding these two factors. The fresh-cooked product was produced using less heat/mechanical processing when compared with the extruded food, and both products used pet-grade ingredients. We see that the fresh-cooked food (Freshpet) had intermediate digestibility values, between the human-grade foods and the extruded food, suggesting a significant effect of processing. However, because of the range of ingredients used in the foods, experimental studies in which ingredient type and processing are carefully controlled are needed to tease out the respective contributions of each.

So, naturally……

What about the Poop?

Dog folks tend to obsess (yeah, a bit) on dog poop. All who regularly walk with our dogs check our dog’s poop for color, form, quality, etc. Moreover, we are all privy to common post-walk queries, such as “How was her poop?” and “Did he have a good poop“?

Crazy, yes, but true.

So, the poop data in this study are certainly of interest to dog folks. When fed the human-grade foods, the dogs produced on average 40 grams (chicken product) or 47 grams (beef product) of feces per day. This can be compared with 64 grams of feces produced when fed the fresh-cooked food and 95 grams when fed the extruded food.

For many dog owners less poop is better right?

Well, to some degree……..

But remember, the logical endpoint of that thinking is that no poop is preferred and that is definitely NOT a goal.

Normal GI functioning in a healthy dog should produce regular, well-formed, easily defecated (i.e. no straining or signs of constipation) feces. High quality ingredients that include some level of fiber support a healthy GI tract and normal defecation. So, while dog folks may be jumping up and down and waving their poop bags into the air at these results, remember that all four of the foods in this study produced normal feces with good fecal quality scores; the extruded food just produced more of it.

That’s all folks! Until the next study!

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Cited Study: Do S, Phungviwatniku T, de Godoy MRC, Swanson KS. Nutrient digestibility and fecal characteristics, microbiota, and metabolites in dogs fed human-grade foods. Journal of Animal Sciences 2021; 99.2: skab028.

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