While the canine body can manufacture some of the amino acids necessary to sustain it, there are ten amino acids which the dog must receive through their food. These are deemed “Essential Amino Acids” and are Arginine, Histidine, Isoleucine, Leucine, Valine, Lysine, Methionine, Phenyalanine, Threonine, and Tryptophan. - with each playing an important role in overall bodily function.

     One of the most commonly occurring amino acids, Arginine is necessary to the production of urea as well as the synthesis of Creatine. It also acts as a vasodilator. Symptoms of Arginine deficiency include hair loss, rash, fatty liver, constipation and poor wound healing. It is interesting to note that humans can, indeed, produce Arginine, while the canine can not.

     While there have been studies that suggest that it can be synthesized by the canine kidney, Histidine is considered “Essential” for both dog and man. Playing the role of protector, it necessary for the repair and growth of tissue, maintenance of myelin sheaths, and aids in production of both red and white blood cells. Deficiencies have been shown to cause cataracts in rats, listlessness, weight loss, reduced activity, and in one study (Bruno Cianciaruso, Michael R. Jones and Joel D. Kopple, American Society for Nutrition ,June 1981), death.

     Isoleucine, Leucine, and Valine (the hydrophobic branched chain amino acids) work in harmony and are necessary for maintenance and recovery of muscle tissue after strenuous activity. Deficiencies of Isoleucine and Leucine cause rapid weight loss and are often mistaken for hypoglycemia as they share symtomology.

     Lysine is perhaps one of the most important amino acids in that it is the building block of all protein in the body. Playing a part in production of hormones, enzymes, antibodies, and aiding in calcium absorption, muscle maintenance, collagen production, deficiencies can cause everything from kidney stone to poor growth, to anemia and fatigue to reproductive dysfunction.

     A lipotropic, Methionine encourages the export of fat from the liver and regulates the amount of sulfur-containing peptides present within the organ. It is these peptides that detoxify and defend the liver from toxic substances. Additionally, Methionine is powerful antioxidant as the sulfur it supplies inactivates free radicals. Deficiency symptoms include skin lesions, slow growth, weakness, edema, and fatty liver.

     Interestingly enough, Phenyalanine is one of the amino acids used in the popular sweetener, Aspertame (NutraSweet) and has been the subject of much controversy. None-the-less, it is naturally occurring in any protein dense foodstuff. Phenyalanine is hydrophobic and found in the lipid portions of cells rather than the aqueous and plays a major part in the transmission of signals from the nerve cells to the brain by aiding in the production of Norepinephrine. Deficiency symptoms are fatigue, diminished appetite, stunted growth, muscle loss and weakness and difficulty in cognitive function.

     Truly muti-functioning, another lipotropic amino acid, Threonine works together with Methionine to clear fats from the liver but, additionally, helps balance protein in the body , aids in the formation of collagen and elastin in the skin, assists in the production of antibodies, and promotes thymus growth and activity. As the effects Threonine are so varied, deficiency symptoms are broad.

     The largest of the amino acids, Tryptophan is probably the most well-known due it’s content in Turkey and post-Thanksgiving meal drowsiness. Actually, Tryptophan serves two major functions - the production of niacin and of serotonin. Deficiency symptoms include dermatitis and diarrhea (in the case of niacin deficiency) and anxiety and weight gain in the case of inadequate serotonin production.

     Given even this very brief overview, it become quite clear that the Essential Amino Acids ought be given high consideration in any attempt at a dog food formulation. The question then becomes how to include these in the formulation in a way that is most efficient given the specificities of the canine.

     Amino acids can be found in both plant and animal matter and, given current science, synthesized in a laboratory. Given customer perception and the trend toward “natural” and organic foods, synthetic amino acids are to be avoided while hydrolyze proteins (proteins that have been broken down into their amino acid components by either prolonged boiling in acid or the use of pancreatic protease) should only be used in the specific cases of prescriptive diets to serve a required need.

     While many pet food manufacturers rely on plant based protein sources in varying degrees due to the great difference in ingredient cost between plant and meat, to rely on these to any great extent actually does the animal and the consumer a dis-service - though not for the reasons usually given by most consumers or on internet message boards. Among these groups, and no doubt due to some very successful marketing efforts, it is usually asserted that vegetative matter is non-digestible and the words “cheap fillers” usually comes up. Actually, vegetative matter, given the extrusion process which gelatinizes the starches, is digestible by the canine as is proven by Leanne N. Twomey, David W. Pethick, James B. Rowe, Mingan Choct, John R. Pluske, Wendy Brown and Maria C. Laviste in their study “The Use of Sorghum and Corn as Alternatives to Rice in Dog Foods “ which was published in The American Society for Nutritional Studies in June 2002. (see: http://jn.nutrition.org/cgi/content/full/132/6/1704S) The dis-service comes in the form of amount of protein, the amount of the Essential Amino Acids, which comprise vegetative matter and the necessity to compensate for these very low concentrations by feeding vastly larger quantities to achieve sufficient maintenance levels.

     Consider, for example, corn - a very common dog food ingredient. The composition of corn is ~3.22% protein per 100 grams and of this protein, less then half (1.39%) is made up of the Essential Amino Acids. A dog would have to eat quite a bit of corn to equal the protein levels in chicken (another very common dog food ingredient) which is ~21.39% protein per 100 grams of which 9.38% is made up of the Essential Amino Acids. Stating this in a very oversimplified manner and recognizing that this does not address varying individual levels of amino acids present, a dog would have to eat approximately 8 times as much corn to gain the same level of Essential Amino Acids as are present in chicken when taken in aggregate. That is a lot of food - and a lot of waste due to increased stool volume! To term vegetative protein sources as inefficient delivery mechanisms for amino acids would not, therefore, be without due cause.

     That using meat protein to deliver the necessary Essential Amino Acids is obvious, given concentration and, therefore, efficacy. Remembering that the goal is to provide the Essential Amino Acids and in sufficient quantity to provide maximum health, the question then becomes one of balance and adequacy as each has a unique amino acid composition.

Please click here for Amino Acid Composition Chart

     It is interesting to note the disparity in Essential Amino Acid composition - most glaring, the total lack of Arginine and Histidine in beef, lamb and pork and, in chicken, the lower levels of each of the amino acids when compared with turkey and pork when exclusive of the Arginine and Histidine. As is seen, turkey has the highest concentration of all Essential Amino Acids.