The idea that using hydrolyzed proteins as a way to combat allergies is an antiquated practice that is all but condemned by most holistic canine nutritionists. Hydrolysis, which breaks down the protein into small components, gives a false sense of security to dog owners. Those who feed these amino acid components in their food(s) of choice recommended by vets (who technically have very limited nutritional training) need to know all the pros and cons. Truthfully, vets get their education on dog food by the companies (Iams, Science Diet, Waltham, Royal Canin, etc) that have created the formula(s) and then send out their reps to sell it to vets.
The theory of hydrolyzed proteins is that when the protein is broken down into such small components, it will no longer be recognized by the immune system as an allergen. Thus, (again in theory) a pet could be fed the same protein that they are allergic to without any allergic reactions. Many food recipes include hydrolyzed yeast as a flavor enhancer as it tends to ‘taste good’ to dogs and humans too. There are no known side effects to hydrolyzed proteins, though it seems to me that there are better ways to attack the food allergy issue as well as the need for flavor enhancers.
With regard to food allergies, using single protein and novel protein foods address the allergy problem head on by removing the allergen entirely from the diet rather than trying to trick the dog’s body. Further, as an advocate of a rotational feeding strategy (rotating your dog’s food for variety and health), I believe this practice truly reduces the chances that your dog will ever develop a food allergy. The rotational diet uses a simple and natural strategy of rotating proteins sources every few months so that your dog’s bodies won’t become overloaded by any single protein. This strategy can not only lower the chances of developing food allergies, but it can increase the chances for a long-term balanced diet as different proteins have different micronutrient profiles.
Most, if not all, hydrolyzed veterinary prescribed foods use flavor enhancers in their dog’s food. This begs the question: why would a dog food containing so-called quality ingredients that are reflective of a dog’s carnivore ancestry (which these foods are not!) even need a flavor boost? Reviewing our data, myself and many other canine nutritionists notice that a majority of the foods that include hydrolyzed proteins are lower quality choices that use plants and fractional meat(s) as their primary protein sources. Your dog is more of a carnivore than an herbivore, so why would you feed any of these cereal-driven (carbohydrate-dominated) foods?
Since there are better and more natural ways to address flavor and allergy issues in dog food, I give hydrolyzed proteins an “F” rating.