Rating: 
Hill’s Prescription Diet D/D Canine dry dog food earns the Advisor’s lowest rating of 1 star.
The Hill’s Prescription Diet D/D line includes 4 dry dog foods.
Although each product appears to have been designed to help with certain skin conditions and digestive issues linked to food allergies, we found no AAFCO nutritional adequacy statements for these dog foods on the Hill’s website.
- 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
Dry Dog Food
Estimated Dry Matter Nutrient Content
Ingredients: Potato, potato starch, duck, potato protein, pork fat (preserved with mixed tocopherols and citric acid), 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 (l-ascorbyl-2-polyphosphate (source of vitamin C), vitamin E supplement, niacin, thiamine mononitrate, vitamin A supplement, calcium pantothenate, biotin, vitamin B12 supplement, pyridoxine hydrochloride, riboflavin, folic acid, vitamin D3 supplement), dl-methionine, vitamin E supplement, taurine, minerals (ferrous sulfate, zinc oxide, copper sulfate, manganous oxide, calcium iodate, sodium selenite), l-tryptophan, preserved with mixed tocopherols and citric acid, phosphoric acid, beta-carotene, rosemary extract
Fiber (estimated dry matter content) = 1.7%
Red items when present indicate controversial ingredients
The first ingredient in this dog food lists potato. Assuming they’re whole, potatoes are a good source of digestible carbohydrates and other healthy nutrients.
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 includes potato starch. Potato starch is a gluten-free carbohydrate, both digestible and hypoallergenic.
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.
This less expensive plant-based ingredient can significantly boost the total protein content reported in this dog food.
The fifth ingredient is pork fat. Commonly known as lard, pork fat can add significant flavor to any dog food. Though it can be high in saturated oils, in reasonable amounts, pork fat can be considered an acceptable ingredient.
The sixth ingredient is soybean oil, red flagged here only due to its suspected (yet unlikely) link to canine food allergies.
Unfortunately, this oil is preserved with butylated hydroxyanisole (a suspected cancer-causing agent) and propyl gallate (a potential reproductive toxin).
This particular oil should not be considered a quality component.
After the natural flavor, we find dicalcium phosphate, a dietary calcium supplement.
Powdered cellulose is a non-digestible plant fiber usually made from cotton or sawdust. Cellulose is sometimes added to dilute the number of calories per serving and to give the feeling of fullness when it is eaten.
Except for the usual benefits of fiber, powdered cellulose provides no nutritional value to a dog.
Fish oil is naturally rich in omega-3 fatty acids, and (depending on the level of its purity) should be considered a healthy 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 have much of an effect on the overall rating of this product.
With three notable exceptions…
First, 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.
Next, we find no evidence of probiotics… friendly bacteria applied to the surface of the kibble after processing.
Finally, the minerals 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 Dry Dog Food
The Bottom Line
Even though this is a prescription product, we continue to limit our judgment to the estimated meat content of the recipe as well as the apparent quality of its ingredients. And nothing else.
Our ratings have nothing to do with the accuracy of claims made by the manufacturer as to this product’s ability to effectively 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 appears to be a below-average dry dog food.
But ingredient quality by itself cannot tell the whole story. We still need to estimate the product’s meat content before determining a final rating.
With so many potato ingredients, it’s difficult to imagine much meat protein being in this Hill’s Prescription Diet D/D Canine product. And a quick look at the numbers should confirm that suspicion.
The dashboard displays a dry matter protein reading of 18%, a fat level of 17% and an estimated carbohydrate content of 57%.
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 serving size of 58% for the overall product line.
Below-average protein. Average fat. And above-average carbs… as compared to a typical dry dog food.
Yet when you consider the protein-boosting effect of the potato protein, this looks like the profile of a dry dog food containing only a modest amount of meat.
Bottom line?
Hill’s Prescription Diet D/D is primarily a potato-based dry dog food using a limited amount of duck, salmon, venison or egg as its main source of animal protein… thus earning the brand one.
Not recommended.
A Final Word
This review is designed to help you make a more informed decision when buying dog food. However, our rating system is not intended to suggest feeding a particular product will result in specific health benefits for your pet.
For a better understanding of how we analyzed this product, please be sure to read our article, “The Problem with Dog Food Reviews”
Remember, no dog food can possibly be appropriate for every life stage, lifestyle or health condition. So, choose wisely. And when in doubt consult a veterinarian for help.
Have an opinion about this dog food… or maybe the review itself? Please know… we welcome your comments.
Notes and Updates
01/03/2010 Original review
08/10/2010 Review updated
11/12/2011 Review updated, no changes
The Dog Food Advisor publishes independent reviews to help pet owners make better choices when shopping for dog food.