Evaluation of zinc-bearing palygorskite effects on the growth, immunity, antioxidant capability, and resistance to transport stress in blunt snout bream (Megalobrama amblycephala)

Abstract

Zn-bearing palygorskite (Zn-Pal), prepared by the ion-exchange method with zinc (Zn) and palygorskite, has attracted attention due to its potential as an antibacterial agent and Zn source in animals. This study aimed to evaluate the effects of dietary Zn-Pal inclusion on growth, immunity, antioxidant capability, and resistance to transport stress in blunt snout bream (BNB). A total of 600 fish of similar size (average body weight, 27.78 ± 0.30 g) were randomly allotted into four groups and fed a basal diet (control group), basal diet supplemented with 90 mg/kg Zn as ZnSO4 or 48 or 90 mg/kg Zn as Zn-Pal. Each diet was tested in five replicates with 30 fish per tank for 60 d. Compared with the control group, Zn-Pal inclusion enhanced the final body weight and feed utilization; increased the blood respiratory burst activity and the activities of plasma alkaline phosphatase, total superoxide dismutase, and copper/zinc superoxide dismutase (Cu/Zn-SOD); decreased the plasma cortisol, lactate and complement 4 (C4) contents; and upregulated the mRNA levels of nuclear factor erythroid 2-related factor 2, catalase, and Cu/Zn-SOD in the hepatopancreas (P < 0.05). Dietary Zn-Pal inclusion enhanced the lysozyme and C4 levels of plasma compared with the ZnSO4 groups (P < 0.05). The inclusion of Zn-Pal in the diet alleviated transportation stress by improving the antioxidant capacity and immunity in BNB. In conclusion, dietary Zn-Pal inclusion increased growth and feed utilization, enhanced immunity and antioxidant capability, and improved resistance to transport stress in BNB. Zn-Pal is better than ZnSO4 as an additive in the diet of BNB.