الفهرس 
Chapter I Introduction and Aim of the workOnly 14 pages are availabe for public view
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Abstract
This study was conducted to evaluate the effect of dietary protein level and amino acid supplementation on the Nile tilapia nursery performance under biofloc system conditions at cold suboptimum temperature. Four experimental diets were carried out; 30% crude protein (CP) diet as a positive control (30P), 22% crude protein (CP) diet as negative control (22P), 22% crude protein (CP( diet supplemented with 1% Lysine (22PL) and 22% crude protein (CP (diet supplemented with 0.5% Threonine (22PT). Formulated diets were tested under biofloc system conditions in three replicates for each treatment. 12 experimental 1000 L tanks were used; each tank was filled with 400 L water and stocked with 50 fingerlings (6.20±0.01 gm. /fish). The experiment was extended for 97 days. Fish fed on a 22PT diet had the highest significantly best values of weight gain (WG), feed intake (FI), feed convergent ratio (FCR), and specific growth rate (SGR) (11.10, 16.95, 1.55 and 1.40, respectively). Also, 22PT diet groups recorded the highest protein content of dried microbial floc and wet whole-body. The lowest total ammonia nitrite (TAN) values were recorded also for the fish groups fed on a 22PT diet. It could be concluded that under biofloc system conditions, a low protein diet supplemented with Threonine can be used as a tool to improve biofloc system performance during tilapia nursery at cold suboptimal water temperature.