The dietary requirement for protein is actually a requirement for aminoacids contained in the protein. It is only in the form of the constituent aminoacids that protein is absorbed from the intestine. Some of the aminoacids are essential in that they have to be provided by the dietary protein or as dietary supplements. Some aminoacids can be produced within the body of the bird by the transformation of other aminoacids. Protein requirement therefore, have two components;

1. The essential aminoacids needed by the bird because it can not synthesize them or synthesize them rapidly enough.
2. Sufficient protein to supply either the non-essential aminoacids themselves or to supply amino nitrogen for their synthesis.

A statement of dietary protein concentration thus provides a convenient means of describing diets and serves as a basis for feed control regulations.

More research is needed in the general area of aminoacid requirement. Currently stated requirement have no reference to environmental conditions. It may generally be assumed that the listed requirements are for a moderate climate (16-24°c). Percentage requirement should probably raised or lowered respectively in warmer or colder environments in accordance with expected differences in feed or energy intakes. Such adjustment might aid in assuring the required daily intake of aminoacids. The aminoacid concentrations presented as requirements are intended to promote maximum growth and production. Maximum economic returns may not however, always be consonant with maximum growth and production, particularly when protein prices are high. The dietary concentrations may accordingly be somewhat reduced, lowering growth rate to some degree, but maintaining economic return.

The productive state of the bird i.e. rate of growth or egg production determines aminoacid requirements per day to meet the requirements for rapid growth. The mature cockerel has a very low requirement compared to the laying hen, even though body size is actually greater than feed consumption is similar.

The genetic constitution of the bird determines body size, growth rate and egg production. Nutrient requirement therefore, differ among breeds because of difference in the efficiency of digestion, nutrient absorption and metabolism of absorbed nutrients.

Dietary protein concentration can affect the requirement for individual essential amino acids. The balance among the essential amino acids, as well as the balance between the concentration of essential and non-essential should be maintained. The maintenance of these optimum balances is extremely important for the efficient utilization of dietary protein. It is desirable to meet the requirements for all the amino acids as closely as possible with avoidance of excess of protein or of individual amino acids.

SPECIFIC AMINOACIDS RELATIONSHIP:

1.METHIONINE AND CYSTINE:

The requirement for methionine can be met only by methionine. The requirement for cystine can be met by cystine or methionine. Methionine readily undergoes metabolic conversion to cystine, whereas the reverse is not possible.

2. PHENYL ALANINE AND TYROSINE:

The requirement for phenylalanine can met only by phenylalanine. The requirement for tyrosine can be met by tyrosine or phenylalanine.

3. GLYCINE AND SERINE:

Glycine and serine can be used interchangeably in poultry diets. Usually when the overall protein requirement is met the amounts of glycine and/or serine are adequate.

(b)ANTAGONISM AND IMBALANCES:

The influence of protein on amino acid requirements may be due to interactions among specific amino acids or amino acid groups. Some interactions commonly referred to as antagonisms occur among amino acids that are actually related e.g; leucine-isoleucine-valine and lysine-arginine. Increasing the dietary level of one or two of a group may increase the requirement for another from the same group. Other interactions referred to as imbalances occur when diets are supplemented with the second limiting amino acid, or all essential amino acid except the limiting amino acid. In some instances e.g.; (threonine imbalances) several amino acids, individually or as group, may

also cause increased need for limiting aminoacid. Antagonism appeared to help a metabolic basis in which the aminoacid(s) present in excess interfere with the retention of other aminoacid(s) of the group. Imbalances cause the blood level of limiting aminoacid to decline without affecting its overall retention. This results in reduced feed intake, the major cause of reduced performance. In supplementing diets with limiting aminoacids it is important to supplement first with the most limiting one, followed by the second most limiting one. Inadvertent over supplementation with only the second most limiting aminoacid may create an imbalance and increase the primary deficiency.

C). CONVERSION OF AMINOACIDS TO VITAMINS:-

Methionine may partly compensate for deficiencies of choline or vitamin B₁₂ by providing needed methionine. Tryptophan may reduce a niacin deficiency through metabolic conversion to niacin. Reliance on these conversions is however, unwise both nutritionally and economically.

AMINOACID AVAILABILITY:

When diets are formulated on the basis of feed analysis data. The assumption is generally made that aminoacids are 80-90 % available from the feedstuff protein. This assumption is necessarily valid. Native proteins vary markedly in their digestibility. Processing of feedstuffs may improve digestibility e.g.; the digestibility of feather protein (keratin) is improved during the manufacture of feather meal. Heat treatment of soybean meal inactivates compounds that interfere with trypsin digestion of protein in the intestine, thereby improving the availability of the aminoacids to the birds. Processing may if not carried out with careful control reduce digestibility of the product. Overheating during the drying of bloodmeal and fishmeal etc., can seriously lower digestibility and the availability of specific aminoacid (of which lysine is probably the most critical under practical conditions of feed formulation).