Effects of dietary onion (Allium cepa) powder on growth performance,hemolymph indices and fillet organoleptic properties of juvenile narrow‐clawed crayfish,Astacus leptodactylus leptodactylus Eschscholtz, 1823

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) on the growth performance, nutritional efficiency indices, hemolymph indices and fillet organoleptic properties of juvenile (5.62 ± 0.39 g) crayfish. The significantly (p < .05) highest values of final weight (71.30 g) and SGR (2.02% per day) and the lowest FCR (1.03) were observed in the juvenile crayfish fed the diet containing 40 g OP/kg. The juvenile crayfish fed the diet containing 40 g OP/kg had the significantly (p < .05) highest THC (105.27 × 10⁵ cell/ml), HC (98.33 × 10⁵ cell/ml), SGC (38.54 × 10⁵ cell/ml) and LGC (49.51 × 10⁵ cell/ml). The crayfish fed the levels of dietary OP higher than 30 g/kg showed the significantly (p < .05) higher values of SOD (4.07–4.30 U/min) and LYZ (6.73–7.20 U/min) compared with those fed 5, 10, 20 and 30 g of dietary OP/kg 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 in crayfish reared in culture conditions.