A 18-week feeding trial was carried out under controlled conditions to compare the effects of onion powder (OP) at six levels (5, 10, 20, 30, 40 and 50 g kg-1) on the growth performance, nutritional efficiency indices, hemolymph indices and fillet organoleptic properties of juvenile (5.62±0.39 g) crayfish. The significantly (p<0.05) highest values of final weight (71.30 g) and SGR (2.02% day-1) and the lowest FCR (1.03) were observed in the juvenile crayfish fed the diet containing 40 g OP kg-1. The juvenile crayfish fed the diet containing 40 g OP kg-1 had the significantly (p<0.05) highest THC (105.27 ×105 cell ml-1), HC (98.33 ×105 cell ml-1), SGC (38.54 ×105 cell ml-1) and LGC (49.51 ×105 cell ml-1). The crayfish fed the levels of dietary OP higher than 30 g kg-1 showed the significantly (p<0.05) higher values of SOD (4.07-4.30 U min-1) and LYZ (6.73-7.20 U min-1) compared with those of fed 5, 10, 20 and 30 g OP kg-1 and control. Polynomial regression of SGR, FCR, PPV and PER suggested that the optimum dietary OP level could be higher than 30 and <50 mg kg-1 in crayfish reared in culture conditions.

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