Proteins are complex molecules which are made up of amino acids and are used as the building blocks for cell growth, maintenance and repair. Carbohydrates provide energy in the form of sugars and are mainly found in plants and grains.
Proteins are made up of 20 amino acids. Dogs can produce about half of these amino acids internally, the other half, termed essential amino acids, need to be provided by the diet. The 10 essential amino acids are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. It is crucial that diet is complete with all of these amino acids as if even one of these “essentials” is deficient, the body cannot make specific proteins effectively.
The biological value of proteins indicates how efficiently an animal utilizes them. For example if egg's value index is 100 in wheat it can be as low as 50. This value is high for proteins from meat, most meat by-products, eggs and dairy products. Dogs can digest these proteins efficiently and they provide amino acids in proportions suitable for tissue protein synthesis. In contrast, the biological value of most plant proteins is low, due to insufficiencies of specific amino acids and lower digestibility.
Carbohydrates typically make up 30-70 percent of a dry dog food. They come mainly from plants and grains, and provide energy in the form of sugars. Carbohydrates have several important functions in a dog food. The most important function of carbohydrates is to provide energy to the animal. Dogs are able to convert certain carbohydrate sources into simple sugars that are easily absorbed. Carbohydrate sources like potato, maize and apples contains fibers that helps to regulate bacteria in the colon. Fiber is not a required nutrient for dogs, but it is included in most dog foods because it helps keep your dog full, maintains colon health, aids digestion, and even helps control blood sugar levels in diabetic dogs.