عنوان مقاله [English]
The amount of lysine required in the diet of juvenile Beluga Huso huso with an average initial weight of 2.45 g was evaluated based on growth response in 12 aerated aquariums in four treatments each with three replications for 40 days. Four diets were prepared based on fish meal with the same protein (39.32%), fat (15.78%) and carbohydrate (21.19%) with different levels of lysine (0, 0.75, 1.5 and 2.25% of dry weight). The diet without lysine was considered as the control diet. Each ration was given in proportion to 4% of body weight, in three equal portions, to groups of three with 10 fish in each replicate. The mean water temperature, dissolved oxygen and pH during the test period were 23.8 ºC, 6.27 mg/L and 7.32, respectively. The results showed a significant difference in the growth performance between the treatments. The maximum weight obtained (31.95 ± 0.84 g) and specific growth rate (7.01 ± 0.09%/day) were observed in the treatment with 2.25% lysine. Apart from the decreased growth in the fish fed the lysine-deficient diet, no signs of growth deficiency were observed in the other fish. Codition factor, food conversion ratio, protein efficiency ratio and survival rate were not significantly different among treatments. Finally, the optimal amount of lysine for this weight group of juvenile Beluga was estimated to be 2.25 g per 100 g of the dry weight of the diet.