WWW.WA S .ORG • WORLD AQUACULTURE • DECEMBER 2022 67 So, the initial focus of nutritional requirement study of most fish species should be on essential amino acid requirements, rather than relatively high protein requirement study. If we consider that high dietary protein means high cost of feed and environmental pollution fromwaste. Moreover, dietary protein with an imbalanced amino acid profile may increase the dietary protein requirement to fulfill the requirement of all the dietary essential amino acids. So, standardization of optimal dietary protein requirement with balanced amino acid profile is necessary. It is not only crucial for animal growth in costeffective manner but also for the reduction of organic load in an ecosystem and environmental pollution (Gaylord et al. 2015). The Ideal Protein Concept The ideal protein can be defined as one that offers the exact balance of amino acids needed for optimum performance and maximum growth. But, dietary essential amino acid (EAA) requirement study using dose-response trials are usually timeconsuming and expensive. However, application of the “ideal protein” concept of Ogino (1980) for estimation of dietary EAA requirements is gaining momentum. According to the ideal protein concept, the ratio between amount of individual body amino acid (A) and the total of essential body amino acids (E) (A/E ratio) remains constant, despite their variation at different stages of development (Portz and Cyrino 2003); however, for implementation of the ideal protein concept, dietary lysine requirement needs to be assessed through a Highlight Points • The ideal protein can be defined as one that offers the exact balance of amino acids needed for optimum performance and maximum growth. • The ideal protein concept can be used to determine the dietary essential amino acid requirement. • The ideal protein concept is useful for the cost-effective feed formulation and minimize systemwaste loading. The progressive development of aquaculture must be continued through the sustainable use of available resources. Moreover, the cost of production is increasing along with the rising cost of the feed. Feed represents 40-60 percent of operational costs and protein is the most expensive nutrient in formulated feeds. The biological value of protein depends on a well-balanced mixture of essential and nonessential amino acids (Wilson 2002). Thus, adequate information on protein requirements of farmed fish is necessary to reduce feed cost, and an adequate supply of essential amino acids is necessary for optimal growth and health. Moreover, dietary replacement of fishmeal with alternative ingredients is trending for cost-effective feed formulation. The increased dependency on alternate proteins with poorer amino acid profiles are highlighting the need of essential amino acid requirement studies. Hence, instead of dietary protein requirement of fish, the initial study should be on essential amino acid requirements followed by optimization of dietary crude protein. A protein requirement study gives the overestimation of dietary crude protein and increases the feed cost and environmental pollution in terms of nitrogenous waste. So, optimization of optimal dietary protein level with a balanced essential amino acid profile including semi-indispensable amino acids (cysteine and tyrosine) is the right approach for fish culture (NRC 2011). Necessity of Protein with Balanced Amino Acid Profile In all living organisms, 20 amino acids are required for protein synthesis in the body. These amino acids are classified as essential and non-essential (Table 1). For those that are essential, fish either cannot synthesized them or can synthesize them inadequately to meet cellular demand. Other dietary amino acids are not essential as they can be synthesized within the body to fulfill all metabolic demands. Protein is the most essential nutrient as it provides the primary source of essential amino acids, source of amino-group for the synthesis of non-essential amino acids and energy when there is a scarcity of non-protein energy sources (NRC 2011). However, fish do not have a specific protein requirement but rather a specific requirement for essential amino acids that are derived from proteins. Ideal Protein with Balanced Amino Acid Profile is Essential in Aquafeed to Prevent Economic Loss and Environmental Deterioration Manas Kumar Maiti and Chetan Kumar Garg TABLE 1. List of essential and non-essential amino acids Es s en t i a l ami no ac i ds Non - e s s en t i a l ami no ac i ds Arginine Alanine Histidine Aspartic acid Isoleucine Asparagine Leucine Cysteine Lysine Glutamic acid Methionine1 Glutamine Phenylalanine2 Glycine Threonine Proline Tryptophan Serine Valine Tyrosine 1 Methionine in cellular metabolism is used to synthesize cysteine. 2 Phenylalanine in cellular metabolism is used to synthesize tyrosine. ( C O N T I N U E D O N P A G E 6 8 )
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