Among the fruits, blueberries and cranberries are the most common in all forms of dog and cat food.
First, the numbers:
Blueberries are found in 29 percent of the dry dog food recipes, 20 percent of dry cat food recipes, 13 percent of wet dog food recipes and 7 percent of wet cat food recipes.
Cranberries almost reverse the percentages, being found in 21 percent of dry dog food recipes, 28 percent of dry cat food recipes, 11 percent of wet dog food recipes and 16 percent of wet cat food.
Why are these ingredients so common? The answer is probably a mixture of science and public opinion.
Blueberries are known as a super food, packed with vitamins and antioxidants, and have become a common ingredient in dog and cat food. Antioxidants are aslo widely used as a means of preserving pet food. Blueberries are also used as a colorant. And blueberries are popular with consumers. Blueberries even show up in the product names of a few dog and cat food products.
Many of the same reasons hold true with cranberries. According to Greg Aldrich, PhD, cranberries are often associated with urinary tract health claims, foods that claim to be fortified with antioxidants, or those that appeal to pet owners looking for added fruits and vegetables. He adds that cranberry juice has been associated with the home remedy for urinary tract infections in people. This reputed treatment has been transferred to pets; typically as a remedy for feline urinary tract disease. He adds that while there may be a thread of truth to this remedy in humans, but whether it holds true for pets has limited evidence so far.
See the Dr. Aldrich's full article on cranberries at Petfood Industry.com.