University of Maryland Extension

Protein: Built by Amino Acids

Proteins are a large complex class of nutrients made up of smaller compounds known as amino acids. In nutrition, amino acids are grouped into two categories depending on their requirement in the diet. Non-dispensable (or essential) amino acids are required in theamino acid diet because the body cannot make them at all or the body cannot make them at a fast enough rate for maximum performance. Dispensable amino acids (non-essential) are generally not required in the food supply because the bird can make an adequate amount of these amino acids to support body proteins. All amino acids are made up of carbon, hydrogen, oxygen and nitrogen (and sometimes sulfur). Animals do not have a requirement for crude protein as such, but enough crude protein must be supplied in the diet to ensure an adequate supply of nitrogen so the body can make nonessential amino acids.

The body is made up of approximately 20% protein. Proteins in feedstuffs are broken down into amino acids by the process of digestion. The amino acids are then absorbed and transported by the blood to the cells that make these amino acids into body proteins. Body proteins are used to build body tissues such as muscles, nerves, cartilage, skin, feathers and beak. Eggs also contain a high percentage of protein.

Dietary proteins not containing the correct proportion of non-dispensable amino acids will not be utilized efficiently to make body proteins. For example, the label on a bag of poultry feed list the percentage of crude protein contained in the feed, but it does not indicate the quality of the protein used. Protein quality is based on how much protein is digestible and utilized after absorption. When poultry nutritionists formulate diets, they will include a variety of feedstuffs that are high in protein because no single feedstuff is able to provide all of the amino acids required in the diet. Some plant sources that are high in protein are soybean meal, canola, cottonseed meal and corn gluten meal.

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