Dietary garlic (Allium sativum) powder improved zootechnical performance, digestive enzymes activity, and innate immunity in narrow-clawed crayfish (Postantacus leptodactylus)

In this study, the dietary effect of garlic powder (GP) as an herbal supplement on the growth performance, digestive enzymes, innate immunity, and antioxidant capacity of narrow-clawed crayfish, Postantacus lep-todactylus, was investigated. In a 90-day feeding trial, the crayfish (N = 360; 25.90 +/- 0.41 g initial weight) were fed with a basal diet (control; GP-free) and supplemented diets with three levels of GP (0.5%, 1%, and 2%). The highest final weight and specific growth rate were obtained in the crayfish fed with GP at 1% and 2% (P < 0.05) and the weight gain in GP 2% treatment was 1.6 fold more than the control group. Also, the feed conversion rate and protein efficiency rate were improved in the GP-add groups compared to the control group (P < 0.05). Furthermore, the highest counts of total hemocyte, large-granular cell, and semi-granular cell were recorded in those fed with GP 2% diet. The crayfish fed GP 2% diet showed the highest and lowest body crude lipid (0.24 +/- 0.03%) and protein contents (15.95 +/- 0.12%), respectively. The highest protease (1.92 +/- 0.03 U/ml) and amylase (8.36 +/- 0.3 U/ml) activities were detected in the crayfish hepatopancreas fed with GP at 2% (P < 0.05). The highest lysozyme activity (21.26 +/- 2.08 U/ml) was observed in the group fed with GP 2% diet, which showed a significant difference from others. Besides, total plasma protein and phenoloxidase activity in the groups fed with GP 1% and GP 2% diets were significantly higher than the control group. Moreover, the activities of superoxide dismutase (79.30 +/- 2.19 U/ml) and nitric oxide synthase (4.16 +/- 0.05 U/ml) in the plasma were significantly increased in GP 2% diet with respect to the GP 0.5% and control groups (P < 0.05). These findings confirmed the beneficial effects of dietary GP, especially at 2%, on growth rate, physiological performance, innate immunity, and antioxidant capacity in P. leptodactylus.