Hill’s Prescription Diet D/D Canine Skin Support dog food is not rated due to its intentional therapeutic design.
The Hill’s Prescription Diet D/D Canine Skin Support product line includes four dry dog foods. However, since we’re unable to locate AAFCO nutritional adequacy statements for these dog foods on the company’s website, it’s impossible for us to report specific life stage recommendations for these recipes.
The following is a list of recipes available at the time of this review.
- Hill’s Prescription Diet D/D Canine Rice and Egg
- Hill’s Prescription Diet D/D Canine Potato and Duck
- Hill’s Prescription Diet D/D Canine Potato and Salmon
- Hill’s Prescription Diet D/D Canine Potato and Venison
Hill’s Prescription Diet D/D Canine Potato and Duck was selected to represent the other products in the line for this review.
Hill's Prescription Diet D/D Canine Potato and Duck
Dry Dog Food
Estimated Dry Matter Nutrient Content
Ingredients: Potato, potato starch, duck, potato protein, pork fat, soybean oil, natural flavor, dicalcium phosphate, lactic acid, fish oil, powdered cellulose, potassium chloride, iodized salt, calcium carbonate, duck by-product meal, choline chloride, vitamins (vitamin E supplement, l-ascorbyl-2-polyphosphate (source of vitamin C), niacin supplement, thiamine mononitrate, vitamin A supplement, calcium pantothenate, biotin, vitamin B12 supplement, pyridoxine hydrochloride, riboflavin supplement, folic acid, vitamin D3 supplement), dl-methionine, taurine, minerals (ferrous sulfate, zinc oxide, copper sulfate, manganous oxide, calcium iodate, sodium selenite) , l-tryptophan, mixed tocopherols added to retain freshness, citric acid added to retain freshness, phosphoric acid, beta-carotene, rosemary extract
Fiber (estimated dry matter content) = 1.7%
Red items when present indicate controversial ingredients
|Estimated Nutrient Content|
|Dry Matter Basis||18%||16%||58%|
|Calorie Weighted Basis||16%||35%||50%|
The first ingredient in this dog food is potato. Potatoes can be considered a gluten-free source of digestible carbohydrates. Yet with the exception of perhaps their caloric content, potatoes are of only modest nutritional value to a dog.
Our only concern here is the amount of potato in this product. Since three of the first four ingredients are all of potato origin, it’s safe to assume potato is the major component in this dog food.
The second ingredient is potato starch. Potato starch is a gluten-free carbohydrate of only modest nutritional value to a dog.
The third ingredient is duck. Although it is a quality item, raw duck contains about 80% water. After cooking, most of that moisture is lost, reducing the meat content to just a fraction of its original weight.
After processing, this item would probably account for a smaller part of the total content of the finished product.
The fourth ingredient is potato protein, the dry residue remaining after removing the starchy part of a potato.
Even though it contains over 80% protein, this ingredient would be expected to have a lower biological value than meat.
And less costly plant-based products like this can notably boost the total protein reported on the label — a factor that must be considered when judging the actual meat content of this dog food.
The fifth ingredient is pork fat, a product from rendering pig meat.
Commonly known as lard, pork fat can add significant flavor to any dog food. And it can be high in linoleic acid, an omega-6 fatty acid essential for life.
Although it may not sound very appetizing, pork fat (in moderate amounts) is actually an acceptable pet food ingredient.
The sixth ingredient soybean oil is red flagged here only due to its rumored (yet unlikely) link to canine food allergies.
However, since soybean oil is high in omega-6 fatty acids and contains no omega-3′s, it’s considered less nutritious than flaxseed oil or a named animal fat.
After the natural flavor, we find dicalcium phosphate, likely used here as a dietary calcium supplement.
The ninth ingredient is lactic acid, a compound found naturally in many living organisms. It’s likely added here to adjust the pH of the product which (in turn) reduces the growth of unwanted biological contaminants.
The tenth ingredient is fish oil. Fish oil is naturally rich in the prized EPA and DHA type of omega-3 fatty acids. These two high quality fats boast the highest bio-availability to dogs and humans.
Depending on its level of freshness and purity, fish oil should be considered a commendable addition.
From here, the list goes on to include a number of other items.
But to be realistic, ingredients located this far down the list (other than nutritional supplements) are not likely to affect the overall rating of this product.
With four notable exceptions…
First, powdered cellulose is a non-digestible plant fiber usually made from the by-products of vegetable processing. Except for the usual benefits of fiber, powdered cellulose provides no nutritional value to a dog.
Next, we note the inclusion of duck by-product meal, a dry rendered product of slaughterhouse waste. It’s made from what’s left of a slaughtered duck after all the prime cuts have been removed.
In a nutshell, duck by-products are those unsavory leftovers usually considered “unfit for human consumption”.
In addition to organs (the nourishing part), this stuff can contain almost anything — feet, beaks, undeveloped eggs — anything except quality skeletal muscle (real meat).
On the brighter side, by-product meals are meat concentrates and contain nearly 300% more protein than fresh duck.
In any case, although this item contains all the amino acids a dog needs, we consider duck by-products an inexpensive, lower quality ingredient.
In addition, we find no mention of probiotics, friendly bacteria applied to the surface of the kibble after processing to help with digestion.
And lastly, the minerals listed here do not appear to be chelated. And that can make them more difficult to absorb. Non-chelated minerals are usually associated with lower quality dog foods.
Hill’s Prescription Diet D/D Dog Food
The Bottom Line
Even though this is a prescription product, our review has nothing to do with the accuracy of claims made by the manufacturer as to the product’s ability to treat or cure a specific health condition.
So, to find out whether or not this dog food is appropriate for your particular pet, you must consult your veterinarian.
With that understanding…
Judging by its ingredients alone, Hill’s Prescription Diet D/D Canine Skin Support looks like a below-average dry dog food.
But ingredient quality by itself cannot tell the whole story. We still prefer to estimate the product’s meat content before concluding our report.
As a group, the brand features an average protein content of 18% and a mean fat level of 16%. Together, these figures suggest a carbohydrate content of 58% for the overall product line.
And a fat-to-protein ratio of about 89%.
Low protein. Near-average fat. And above-average carbs when compared to a typical dry dog food.
When you consider the protein-boosting effect of the potato protein, this looks like the profile of a kibble containing a limited amount of meat.
Hill’s Prescription Diet D/D Canine Skin Support is a plant-based dry dog food using a limited amount of duck, salmon, venison or egg product as its main sources of animal protein.
However, due to its intentional therapeutic design, this dog food is not rated.
Rice ingredients can sometimes contain arsenic. Until the US FDA establishes safe upper levels for arsenic content, pet owners may wish to limit the total amount of rice fed in a dog's daily diet.
A Final Word
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Notes and Updates
01/03/2010 Original review
08/10/2010 Review updated
11/12/2011 Review updated
05/14/2013 Review updated
05/14/2013 Last Update