Dietary protein

june 18

Source of protein
1. Animal
2. Plant (limited amount to use in feed than animal source because plant protein source are: Effected on non-balance of amino acid in feed and have anti-nutrition factor substance which effected on abnormality of enzyme function, nervous system and growth

– Source of nitrogen for constructing amino acids and proteins in fish (enzyme, hormone, Immune substance, genetic substance etc.)
– For build and repair tissues of body protein
– Protein is also can used as an energy source for metabolism (but not economic, expensive to use there should be use as a source for growth).
– The protein required for body protein maintenance is called the minimum protein requirement or maintenance requirement

The optimum protein level is not precise because it depends on a number of factors, such as:
– Natural foods
– Trophic level
– Life stage of the fish
– Feeding level
– The composition and ratio of amino acid
– Energy content of the food & degree of protein sparing

An adequate supply of dietary protein is essential for fish to thrive and grow well. For most animals, the protein requirements are considered to be the sum of the requirements for individual EAA and the requirement for non essential nitrogen, although attempts have been made with many species of fish to establish an optimal dietary protein level. Theoretically, fish do not have a dietary requirement for protein per se, but they do require a dietary supply of certain EAA that contribute to protein structure. However, fish do not require only protein but the important thing is the amino acid composition of feed because there will be effect on imbalance amino acid that contribute to protein structure

If fish fed feed with non-protein energy not enough or lower protein content, it will be deaminate from body to use in metabolism. Fish and shrimp eat primarily to satisfy energy requirement, so diet with excess energy content will inhibit food intake and also reduce the protein available for growth. Thus if energy/protein ratio is too low, protein will be used to satisfy energy requirement first. However, at higher moderate dietary energy lead to deposition of carcass lipid and undesired change in carcass composition. The design of practical feed is therefore a compromise between a protein level that produce good growth but does not result in undesired highly levels of carcass lipid.

recapped from P.Somsueb


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