Rating: 
Hill’s Science Diet Adult dry dog food earns the Advisor’s second-lowest rating of 2.5 stars.
The Hill’s Science Diet Adult dry product line includes 23 kibbles.
Although we could not locate AAFCO nutritional adequacy statements for these products on the Hill’s website, each product appears to be designed for a specific life stage, lifestyle, breed size or activity level.
- Hill’s Science Diet Adult Active
- Hill’s Science Diet Adult Oral Care
- Hill’s Science Diet Adult Small Bites
- Hill’s Science Diet Adult Large Breed
- Hill’s Science Diet Adult High Energy
- Hill’s Science Diets Advanced Fitness
- Hill’s Science Diet Adult Light (1.5 stars)
- Hill’s Science Diet Adult Sensitive Skin
- Hill’s Science Diet Adult Healthy Mobility
- Hill’s Science Diet Mature Adult (1 star)
- Hill’s Science Diet Adult Sensitive Stomach
- Hill’s Science Diet Adult Lamb Meal and Rice
- Hill’s Science Diet Adult Small and Toy Breed
- Hill’s Science Diet Adult Healthy Mobility Small Bites
- Hill’s Science Diet Adult Healthy Mobility Large Breed
- Hill’s Science Diet Adult Lamb Meal and Rice Small Bites
- Hill’s Science Diet Adult Lamb Meal and Rice Large Breed
Because of their lower ratings, the Adult Light and Mature Adult products are covered in their own special reports.
Hill’s Science Diet Adult Large Breed dry dog food was selected to represent the others in the line for this review.
Hill's Science Diet Adult Large Breed
Dry Dog Food
Estimated Dry Matter Nutrient Content
Ingredients: Whole grain corn, chicken by-product meal, soybean meal, animal fat (preserved with mixed tocopherols and citric acid), soybean oil, chicken liver flavor, lactic acid, flaxseed, iodized salt, dried chicken cartilage, 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), vitamin E supplement, taurine, potassium chloride, minerals (ferrous sulfate, zinc oxide, copper sulfate, manganous oxide, calcium iodate, sodium selenite), l-carnitine, preserved with mixed tocopherols and citric acid, phosphoric acid, beta-carotene, rosemary extract
Fiber (estimated dry matter content) = 1.8%
Red items when present indicate controversial ingredients
The first ingredient in this dog food is corn. Corn is an inexpensive and controversial cereal grain of only modest nutritional value to a dog.
For this reason, we do not consider corn a preferred component in any dog food.
The second item lists chicken by-product meal, a dry rendered product of slaughterhouse waste. It’s made from what’s left of a slaughtered chicken after all the prime cuts have been removed.
In a nutshell, chicken 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 chicken.
The third ingredient is soybean meal. Soybean meal is actually a useful by-product. It’s what remains of soybeans after all the oil has been removed.
Soybean meal contains 48% protein. However, compared to meat, this item is considered an inferior plant-based protein providing a lower biological value.
The fourth item is animal fat. Animal fat is a generic by-product of rendering, the same high-temperature process used to make meat meals.
Since there’s no mention of a specific animal, this item could come from almost anywhere: restaurant grease, slaughterhouse waste, diseased cattle — even euthanized pets.
We do not consider generic animal fat a quality ingredient.
The fifth ingredient is soybean oil, red flagged here only due to its controversial (yet unlikely) link to canine food allergies.
After the chicken liver flavor, we find lactic acid, a nutrient found naturally in many living organisms.
It’s difficult to say with certainty why lactic acid is present here except to presume it’s added to balance the pH of the recipe.
The eighth ingredient is flaxseed, one of the best plant sources of healthy omega-3 fatty acids. Provided they’ve first been ground into a meal, flax seeds are also rich in soluble fiber.
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 two notable exceptions…
First, we find no evidence of probiotics, friendly bacteria applied to the surface of the kibble after processing.
And 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 Science Diet Adult Dry Dog Food
The Bottom Line
Judging by its ingredients alone, Hill’s Science Diet Adult 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.
The dashboard displays a dry matter protein reading of 25%, a fat level of 16% and an estimated carbohydrate content of 51%.
When we exclude the Adult Light and Mature Adult lines, the brand features an average protein content of 25% and a mean fat level of 17%. Together, these figures suggest a carbohydrate serving size of 50% for the overall product line.
Below-average protein. Near-average fat and above-average carbs when compared to a typical dry dog food.
Yet when you consider the protein-boosting effect of the soy meal or the corn gluten meal (in many of the other recipes), this looks like the profile of a kibble containing only a modest amount of meat.
Bottom line?
Hill’s Science Diet Adult is a grain-based dry dog food using only a modest amount of chicken by-product or lamb meals as its main sources of animal protein, thus earning the brand 2.5 stars.
Not recommended.
Those looking for a wet product from the same company may wish to visit our review of Hill’s Science Diet Adult canned dog food.
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
12/27/2009 Original review
08/01/2010 Review updated
11/21/2011 Review updated
The Dog Food Advisor publishes independent reviews to help pet owners make better choices when shopping for dog food.