Proteins are groups of amino acids linked to each other in different quantities and sequences. Each protein has a combination and arrangement of amino acids that is unique. Your dog breaks down these proteins to form free amino acids which are then absorbed into the bloodstream and distributed to all cells of the body, where they are used to build body proteins.

Over twenty amino acids are used in the body. Ten of these must be supplied in the diet for dogs. Nonessential amino acids are those that the body can produce in sufficient amounts from other sources and, thus, do not need to be supplied in the diet.

Protein Requirements of Dogs
A dog's protein requirement depends upon the life stage and activity of the dog. Generally, puppies need more dietary protein than do adult dogs. At the other age extreme, research has shown that geriatric dogs can benefit from a protein level of 25 percent or more.

Animals maintained with inadequate protein reserves are more susceptible to stresses and that may render the animal more susceptible to infections and other maladies.

Research shows that a diet of 25 percent protein with reduced calories from fat is most beneficial for weight loss.

Sources
Proteins are derived from both animal and plant sources. Most proteins contain inadequate amounts of one or more amino acids and shouldn’t be the only protein source in a diet. Therefore, it is important to balance out these deficiencies and/or excesses of amino acids when selecting ingredients for use in pet food diets.

For example, soybean meal and corn complement each other perfectly, because the amino acids which are deficient in one are present in the other. Neither meat nor soybean meal is an ideal protein alone, and should be balanced with another complementary source of amino acids.

Protein Digestibility
As important as the quality and amount of protein is its digestibility. A dog’s body might not be able to use all the protein present in a food, so it is important that the amount that can be used is enough.

Quality control during pet food processing is important. Protein may be damaged by heat processing, but most reputable pet food manufacturers use proper cooking methods and employ quality control measures to ensure that products are made properly. Because information about protein digestibility cannot be listed on pet food labels, the manufacturer's reputation is important.