الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Currently, one of the major problems facing the aquaculture industry is increasing the cost of fish feed. Feed cost plays a critical role since it represents approximately 40–60% of the total production cost, especially in intensive culture systems. Protein alone constitutes about 50% of the feed cost, being the most expensive ingredient in aqua feeds. Generally, fishmeal (FM) is considered to be the main source of dietary protein for most commercially farmed fish species because of its high content of protein and its balanced amino acid composition. Moreover, FM is an excellent source of essential fatty acids (EFAs), digestible energy, minerals, and vitamins. However, with the rapid growth of aquaculture and increasing demand for FM from the animal feed industry, the cost of FM has extremely increased. Therefore, it has become essential for aquaculture production systems to reduce their reliance on FM by using less expensive protein ingredients and/or reducing dietary protein levels in fish diets, but in both cases, the deficiency in some essential amino acids, which are known as “limiting amino acids” will be the most prominent concern. The strategy of synthetic amino acid supplementation has been widely used in tilapia diet formulation based on the ideal concept to ensure a well-balanced amino acid profile for optimum growth performance. Therefore, the aim of this study focused on evaluating the effect of reducing dietary protein levels in Nile tilapia (Oreochromis niloticus) with dietary supplementation of commercially-available synthetic amino acids at different levels (100 and 120% NRC, 1993). The results of our study confirmed that in Nile tilapia practical diets, dietary protein content could be reduced from 32 to 26% with IAA supplementation at 120% of the NRC nutritional recommendation while maintaining comparable tilapia growth, body composition, immune response, antioxidant activity, and healthiness of the internal organs and also our results confirmed that Nile tilapia can utilize synthetic amino acids efficiently to restore the IAA balance in the low protein diets and promotes optimal growth performance.