An excellent article on the need for protein in dog foods appeared in the July/August issue of Ducks Unlimited. The author discussed how the dog's need for protein is based on the animal's age, condition and level of physical activity. Of special note were the author's comments on comparing vegetable and animal proteins for use in dog rations: "Dogs are not carnivores, they are omnivores - animals that get their protein from both plant and animals. The quality of protein in any dog food - in other words, how the amino acids are balanced - is generally more important than where those acids come from. Soy protein, for instance, is nutritionally equivalent or even superior to animal protein, and provides most of the 10 essential amino acids. Nor is it difficult to digest. In fact, according to Purina, poor quality meat or poultry meals are less digestible than soybean meal. Poultry by-product meals have a relatively high protein count, but need to be balanced with other protein to provide a complete assay of the essential amino acids. The same holds true for cereal grains such as corn and wheat. Corn and soybean meals complement each other almost perfectly, since the amino acids absent in one are present in the other. Other grains, such as barley and wheat are added to dog foods as a source of carbohydrates".

Carty, Dave. 1999. Protein's pros and cons. Ducks Unlimited. July/August issue, p26.